Add next-steps prompt to refine-plan skill

[williamthorsen]

Problem

When refine-plan and save-plan complete, they report artifact paths and stop. The user — often context-switching between terminals — gets no prompt suggesting what to do next. By contrast, design-and-plan ends with a structured next-steps block, but it uses /skill-name syntax that is Claude Code-specific and doesn't port to other platforms.

A related gap (#325): when refine-plan produces a revision that changes the solution approach, the source ticket may become stale, but no prompt is offered to update it.

Context

• design-and-plan Phase 5 (lines 199–215) defines the existing next-steps pattern with /skill-name syntax
• refine-plan ends with a bare path report at step 6
• save-plan ends with "Report the file path. Nothing else."
• The _data/ directory holds shared reference data referenced via Markdown links (artifact-conventions.md, branch-format.md, etc.)
• The next-steps options are identical across all three skills; only the recommendation context differs

Solution

Shared data file: _data/next-steps-after-plan.md

Extract the next-steps block into a shared reference file defining:

• Options: refine plan, orchestrate dev, implement directly
• Format: ▶ for recommended, · for others; platform-agnostic skill invocation (Use the skill-name skill with plan: {path}, ticket: {path})
• Recommendation rules (priority-ordered, evaluate top to bottom):
  1. Refine — the plan is unreviewed and the work is non-trivial, OR the review surfaced significant scope changes or unresolved questions
  2. Orchestrate — the plan involves non-trivial code changes
  3. Implement directly — the work is trivially simple, prose-only, or a single well-understood change
  • When uncertain, recommend the more thorough option.

Output format:

Next steps:
  ▶ Use the `orchestrate-dev` skill with plan: {plan_path}, ticket: {ticket_source} (recommended)
  · Use the `refine-plan` skill with plan: {plan_path}, ticket: {ticket_source}
  · Implement directly

Update design-and-plan

Replace the inline next-steps block (lines 199–215) with a reference to the shared file. Replace /skill-name syntax with the platform-agnostic format. Add ticket path to the output.

Update refine-plan

Add two things to step 6 (Report completion):

1. Conditional ticket-update prompt (Prompt to update ticket after refine-plan results in changes #325): when the revision materially changed the approach, compare with the source ticket and offer to update it. This is skill-specific logic, not shared.
2. Next-steps block referencing the shared file.

Update save-plan

Replace the terse completion with:

1. Report the file path (keep this)
2. Conditional prompt to create or update a ticket (skill-specific)
3. Next-steps block referencing the shared file

Not shared

• Ticket prompts — different trigger logic per skill, not worth parameterizing
• Recommendation context — each skill supplies its own (plan reviewed vs. unreviewed, review findings severity, etc.)

Acceptance criteria

• _data/next-steps-after-plan.md exists with options, format, and recommendation rules
• design-and-plan references the shared file; output uses platform-agnostic format with ▶/· markers and includes ticket path
• refine-plan ends with a next-steps prompt matching the shared format
• refine-plan prompts to update the ticket when the revision changed the approach (Prompt to update ticket after refine-plan results in changes #325)
• save-plan ends with a ticket prompt followed by a next-steps prompt
• All three skills mark exactly one option with ▶ and "(recommended)"
• No skill uses /skill-name syntax in next-steps output

Subsumes #325.