Subagent-injected skills are not deployed by sync's closure resolver

[williamthorsen]

Problem

resolveClosure (packages/agents/src/lib/dependency-resolver.ts) follows only dependencies: and members: edges. A subagent's top-level skills: field — the runtime injection list telling the harness which skills to load into the subagent's context — is invisible to it. A skill named only in skills: is injected at runtime but never pulled into the set of files sync deploys, so a selectively-synced subagent can reference a skill that was never materialized.

Context

The @library collection masks the gap: it resolves to every skill, so sync --global deploys them all. The gap bites a project that selectively deploys a subagent via repo sync without that skill otherwise in its closure. All 10 shipped subagents that declare skills: omit a matching dependencies: edge, so the "declare it in two places" workaround is reliably missed. Surfaced while reviewing #880, where the authoring-guidance rulebook documents that workaround.

Proposed solution

Union a subagent's top-level skills: into its skill edges in resolveClosure — not retrofit a dependencies: edge onto each subagent, which the 10/10 omission rate shows authors won't maintain. The resolver's existing visit bookkeeping carries dedup and cycle-safety, so a skill named in both skills: and dependencies: resolves once. An injected skill absent from the library fails sync closed, the same as any other missing edge.

Acceptance criteria

Must have

• resolveClosure unions a subagent's top-level skills: field into its skill edges, so injected skills enter the deployment closure without a separate dependencies: declaration.
• A subagent deployed via selective repo sync materializes its injected skills even when they are not otherwise in the closure.
• Dedup and cycle detection still hold with the added edges.
• The new resolver behavior is covered by tests.

Should have

• The authoring-guidance rulebook no longer presents an injected skills: entry as needing a paired dependencies: edge — both the "Declaring dependencies" section opener and the subagent frontmatter bullet are corrected.