feat: sync upstream mattpocock/skills + add /teach command

commands/teach.md

@@ -0,0 +1,6 @@
+---
+description: Teach the user a new skill or concept over multiple sessions, using the current directory as a stateful teaching workspace.
+arguments: [{ name: "topic", description: "What you'd like to learn about. If omitted, the agent will interview you to define the mission.", required: false }]
+---
+
+Load the `teach` skill and follow its instructions.

upstream/.claude-plugin/plugin.json

@@ -14,6 +14,7 @@
     "./skills/productivity/caveman",
     "./skills/productivity/grill-me",
     "./skills/productivity/handoff",
+    "./skills/productivity/teach",
     "./skills/productivity/write-a-skill"
   ]
 }

upstream/README.md

@@ -164,6 +164,7 @@ General workflow tools, not code-specific.
 - **[caveman](./skills/productivity/caveman/SKILL.md)** — Ultra-compressed communication mode. Cuts token usage ~75% by dropping filler while keeping full technical accuracy.
 - **[grill-me](./skills/productivity/grill-me/SKILL.md)** — Get relentlessly interviewed about a plan or design until every branch of the decision tree is resolved.
 - **[handoff](./skills/productivity/handoff/SKILL.md)** — Compact the current conversation into a handoff document so another agent can continue the work.
+- **[teach](./skills/productivity/teach/SKILL.md)** — Teach the user a new skill or concept over multiple sessions, using the current directory as a stateful teaching workspace.
 - **[write-a-skill](./skills/productivity/write-a-skill/SKILL.md)** — Create new skills with proper structure, progressive disclosure, and bundled resources.
 
 ### Misc

upstream/skills/engineering/grill-with-docs/CONTEXT-FORMAT.md

@@ -24,13 +24,10 @@ _Avoid_: Client, buyer, account
 
 ## Rules
 
-- **Be opinionated.** When multiple words exist for the same concept, pick the best one and list the others as aliases to avoid.
-- **Flag conflicts explicitly.** If a term is used ambiguously, call it out in "Flagged ambiguities" with a clear resolution.
+- **Be opinionated.** When multiple words exist for the same concept, pick the best one and list the others under `_Avoid_`.
 - **Keep definitions tight.** One or two sentences max. Define what it IS, not what it does.
-- **Show relationships.** Use bold term names and express cardinality where obvious.
 - **Only include terms specific to this project's context.** General programming concepts (timeouts, error types, utility patterns) don't belong even if the project uses them extensively. Before adding a term, ask: is this a concept unique to this context, or a general programming concept? Only the former belongs.
 - **Group terms under subheadings** when natural clusters emerge. If all terms belong to a single cohesive area, a flat list is fine.
-- **Write an example dialogue.** A conversation between a dev and a domain expert that demonstrates how the terms interact naturally and clarifies boundaries between related concepts.
 
 ## Single vs multi-context repos
 

upstream/skills/engineering/to-prd/SKILL.md

@@ -11,11 +11,9 @@ The issue tracker and triage label vocabulary should have been provided to you 
 
 1. Explore the repo to understand the current state of the codebase, if you haven't already. Use the project's domain glossary vocabulary throughout the PRD, and respect any ADRs in the area you're touching.
 
-2. Sketch out the major modules you will need to build or modify to complete the implementation. Actively look for opportunities to extract deep modules that can be tested in isolation.
+2. Sketch out the seams at which you're going to test the feature. Existing seams should be preferred to new ones. Use the highest seam possible. If new seams are needed, propose them at the highest point you can.
 
-A deep module (as opposed to a shallow module) is one which encapsulates a lot of functionality in a simple, testable interface which rarely changes.
-
-Check with the user that these modules match their expectations. Check with the user which modules they want tests written for.
+Check with the user that these seams match their expectations.
 
 3. Write the PRD using the template below, then publish it to the project issue tracker. Apply the `ready-for-agent` triage label - no need for additional triage.
 

upstream/skills/productivity/README.md

@@ -5,4 +5,5 @@ General workflow tools, not code-specific.
 - **[caveman](./caveman/SKILL.md)** — Ultra-compressed communication mode. Cuts token usage ~75% by dropping filler while keeping full technical accuracy.
 - **[grill-me](./grill-me/SKILL.md)** — Get relentlessly interviewed about a plan or design until every branch of the decision tree is resolved.
 - **[handoff](./handoff/SKILL.md)** — Compact the current conversation into a handoff document so another agent can continue the work.
+- **[teach](./teach/SKILL.md)** — Teach the user a new skill or concept over multiple sessions, using the current directory as a stateful teaching workspace.
 - **[write-a-skill](./write-a-skill/SKILL.md)** — Create new skills with proper structure, progressive disclosure, and bundled resources.

upstream/skills/productivity/teach/GLOSSARY-FORMAT.md

@@ -0,0 +1,35 @@
+# GLOSSARY.md Format
+
+`GLOSSARY.md` is the canonical language for this teaching workspace. All explainers, exercises, and learning records should adhere to its terminology. Building it is itself part of learning: compressing a concept into a tight definition is evidence the user understands it.
+
+## Structure
+
+```md
+# {Topic} Glossary
+
+{One or two sentence description of the topic this glossary covers.}
+
+## Terms
+
+**Hypertrophy**:
+Muscle growth driven by mechanical tension and metabolic stress over repeated training sessions.
+_Avoid_: Bulking, getting big
+
+**Progressive overload**:
+Systematically increasing the demand on a muscle over time — via load, volume, or intensity.
+_Avoid_: Pushing harder, levelling up
+
+**RPE (Rate of Perceived Exertion)**:
+A 1–10 self-rating of how hard a set felt, where 10 is failure and 8 means two reps left in the tank.
+_Avoid_: Effort score, intensity rating
+```
+
+## Rules
+
+- **Add a term only when the user understands it.** The glossary is a record of compressed knowledge, not a dictionary the user reads to learn. If the user has just been introduced to a concept, wait until they can use it correctly before promoting it here.
+- **Be opinionated.** When several words exist for the same concept, pick the best one and list the rest as aliases to avoid. This is how language compresses.
+- **Keep definitions tight.** One or two sentences. Define what the term IS, not what it does or how to do it.
+- **Use the glossary's own terms inside definitions.** Once a term is in the glossary, prefer it everywhere — including inside other definitions. This is what makes complex terms easier to grasp later.
+- **Group under subheadings** when natural clusters emerge (e.g. `## Anatomy`, `## Programming`). A flat list is fine when terms cohere.
+- **Flag ambiguities explicitly.** If a term is used loosely in the wider field, note the resolution: "In this workspace, 'set' always means a working set — warm-ups are tracked separately."
+- **Revise as understanding deepens.** A definition the user wrote in week one may be wrong by week six. Update in place; do not leave stale entries.

upstream/skills/productivity/teach/LEARNING-RECORD-FORMAT.md

@@ -0,0 +1,46 @@
+# Learning Record Format
+
+Learning records live in `./learning-records/` and use sequential numbering: `0001-slug.md`, `0002-slug.md`, etc. Create the directory lazily — only when the first record is written.
+
+They are the teaching equivalent of ADRs: they capture non-obvious lessons, key insights, and stated prior knowledge that will steer future sessions. They are used to calculate the zone of proximal development.
+
+## Template
+
+```md
+# {Short title of what was learned or established}
+
+{1-3 sentences: what was learned (or what prior knowledge was established), and why it matters for future sessions.}
+```
+
+That is the whole format. A learning record can be a single paragraph. The value is recording _that_ this is now known and _why_ it changes what to teach next — not in filling out sections.
+
+## Optional sections
+
+Only include these when they add genuine value. Most records won't need them.
+
+- **Status** frontmatter (`active | superseded by LR-NNNN`) — useful when an earlier understanding turns out to be wrong and is replaced.
+- **Evidence** — how the user demonstrated the understanding (a question answered, an exercise completed, prior experience cited). Useful when the claim might be revisited.
+- **Implications** — what this unlocks or rules out for future sessions. Worth recording when non-obvious.
+
+## Numbering
+
+Scan `./learning-records/` for the highest existing number and increment by one.
+
+## When to write a learning record
+
+Write one when any of these is true:
+
+1. **The user demonstrated genuine understanding of something non-trivial** — not just exposure, but evidence they can use the concept correctly. This sets a new floor for what to teach next.
+2. **The user disclosed prior knowledge** — "I already know X." Record it so future sessions don't re-teach it. Also record the _depth_ claimed.
+3. **A misconception was corrected** — the user previously believed something wrong and now sees why. These are high-value: they predict future stumbling blocks for related topics.
+4. **The mission shifted in response to learning** — the user discovered they cared about something different than they thought. Cross-link to [[MISSION.md]] and update it.
+
+### What does _not_ qualify
+
+- Material that was merely covered. Coverage is not learning. Wait for evidence.
+- Anything already captured tersely in [[GLOSSARY.md]] as a term definition. Don't duplicate.
+- Session-by-session activity logs. Learning records are not a journal — they are decision-grade insights.
+
+## Supersession
+
+When a later record contradicts an earlier one (the user's understanding deepened or corrected), mark the old record `Status: superseded by LR-NNNN` rather than deleting it. The history of how understanding evolved is itself useful signal.

upstream/skills/productivity/teach/MISSION-FORMAT.md

@@ -0,0 +1,31 @@
+# MISSION.md Format
+
+`MISSION.md` lives at the workspace root. It captures the _reason_ the user is learning this topic. Every teaching decision — what to teach next, which resources to surface, which exercises to design — should trace back to this document.
+
+## Template
+
+```md
+# Mission: {Topic}
+
+## Why
+{1-3 sentences. The concrete real-world goal the user is chasing. What changes in their life or work when they have this skill? Avoid abstract framings like "to understand X" — push for the underlying outcome.}
+
+## Success looks like
+- {A specific, observable thing the user will be able to do}
+- {Another specific thing}
+- {…}
+
+## Constraints
+- {Time, budget, prior commitments, learning preferences, anything that bounds the approach}
+
+## Out of scope
+- {Adjacent topics the user explicitly does not want to chase right now — protects the zone of proximal development}
+```
+
+## Rules
+
+- **One mission per workspace.** If the user wants to learn two unrelated things, that is two workspaces.
+- **Concrete over abstract.** "Run a half marathon by October" beats "get fitter." "Ship a Rust CLI to my team" beats "learn Rust."
+- **Push back on vagueness.** If the user cannot articulate why, interview them before writing anything. A bad mission is worse than no mission.
+- **Revise when reality shifts.** Missions change. When the user's goal moves, update this file — don't leave a stale mission steering future sessions.
+- **Keep it short.** If `MISSION.md` runs past a screen, it has stopped being a compass and started being a plan.

upstream/skills/productivity/teach/RESOURCES-FORMAT.md

@@ -0,0 +1,32 @@
+# RESOURCES.md Format
+
+`RESOURCES.md` is the curated set of trusted sources for this topic. Knowledge for explainers should be drawn from here, not from parametric guesses. Wisdom comes from the communities listed here.
+
+## Structure
+
+```md
+# {Topic} Resources
+
+## Knowledge
+
+- [Book: _The Science and Practice of Strength Training_ — Zatsiorsky & Kraemer](https://example.com)
+  Foundational text on programming and adaptation. Use for: anything to do with periodisation, recovery, intensity zones.
+- [Article: "How Much Should I Train?" — Greg Nuckols (Stronger By Science)](https://example.com)
+  Evidence-based review of volume landmarks. Use for: weekly set targets per muscle group.
+
+## Wisdom (Communities)
+
+- [r/weightroom](https://reddit.com/r/weightroom)
+  High-signal subreddit, moderated against bro-science. Use for: programme critique, plateau troubleshooting.
+- Local: Tuesday strength class at {gym name}
+  Use for: real-time coaching feedback on lifts.
+```
+
+## Rules
+
+- **High-trust only.** Prefer primary sources, recognised experts, peer-reviewed work, and communities with strong moderation. If a resource is marketing dressed as education, leave it out.
+- **Annotate every entry.** A bare link is useless in three months. Add one line: what it covers and when to reach for it.
+- **Group by Knowledge / Wisdom.** Mirrors the philosophy in [SKILL.md](./SKILL.md). It is fine for a resource to appear in only one group.
+- **Surface gaps explicitly.** If no good resource exists for an area the mission needs, write a `## Gaps` section listing what is missing. This drives future search.
+- **Prune ruthlessly.** A resource that turned out to be wrong, shallow, or off-mission should be removed, not buried. Better five sharp sources than thirty mediocre ones.
+- **Record community preferences.** If the user has opted out of joining communities, note it here so future sessions don't keep proposing them.