fix(agent-help): wire skills metas and correct 'plugin skills' command labels

[christso]

Summary

Fixes two related defects in the --agent-help surface for the skills subcommand group:

1. skillsListMeta, skillsAddMeta, and skillsRemoveMeta were defined in src/cli/metadata/plugin-skills.ts but never imported by src/cli/agent-help.ts, so AI agents could not discover the skills list / add / remove commands at all.
2. Each meta's command field was labeled 'plugin skills *', but the runtime command path is 'skills *' because skillsCmd is registered as a top-level group in src/cli/index.ts. Same drift was present in the --json envelopes and the --plugin ambiguity-hint strings inside the handlers.

Changes

• src/cli/agent-help.ts: import and add skillsListMeta, skillsAddMeta, skillsRemoveMeta to allCommands.
• src/cli/metadata/plugin-skills.ts: rename command values to 'skills *'. Updated examples: entries to match.
• src/cli/commands/plugin-skills.ts: update every jsonOutput({ ..., command: 'plugin skills X' ... }) and the in-message hint strings to use the runtime path.
• tests/unit/cli/agent-help.test.ts: include the three new metas in the test fixture and bump expected count from 13 → 16.

Test plan

• bun run build succeeds
• bun test — 1191 pass / 0 fail
• Verification gate from the issue passes end-to-end:
  • allagents --agent-help | jq -e '.commands | map(.command) | contains(["skills list", "skills add", "skills remove"])' → true
  • allagents --agent-help "skills list" | jq -e '.command == "skills list"' → true (and same for add / remove)
  • allagents --json skills list | jq -e '.command == "skills list"' → true
  • grep "'plugin skills " src/cli/metadata/plugin-skills.ts → no matches

Closes #371

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View logs

[christso]

Code Review: ✅ APPROVE (with one non-blocking suggestion)

Correctness

Both defects from #371 are addressed:

1. agent-help.ts::allCommands now imports and includes skillsListMeta, skillsAddMeta, skillsRemoveMeta.
2. The command: labels in both plugin-skills.ts metadata and the JSON envelope error/success paths are now 'skills *', matching the runtime registration in src/cli/index.ts.

All 16 jsonOutput({...}) call sites in commands/plugin-skills.ts were updated consistently. The two ambiguity-hint error strings (Use --plugin to specify: allagents skills <add|remove> ...) were also updated, keeping user-facing tips consistent with the runtime path.

CLAUDE.md compliance

• Conventional commit title (fix(agent-help): ...) ✓
• No Co-Authored-By ✓
• Test added/updated alongside the change ✓
• One-test-per-distinct-path principle respected ✓

Verification gate

All four checks from the issue are covered.

Non-blocking suggestion (follow-up)

The issue's Implementation notes explicitly recommended:

Add a unit test that asserts every AgentCommandMeta.command resolves to a real command path in the cmd-ts tree. This guards against future drift between metadata and runtime registration.

This guardrail is not in this PR — the new tests only assert the metadata array has 16 entries and contains the three new ones, which would still pass if a future meta drifted from its registered command (i.e., the exact class of bug being fixed here). Consider a follow-up agent-help-drift.test.ts that walks the cmd-ts tree and asserts every meta.command maps to a real subcommand chain. Not blocking — the immediate fix is correct.

[christso]

Superseded by #380 (skill rename) which landed first and includes all of this PR's changes (metas wired into agent-help + corrected command labels) under the new singular form.