feat(skills): unified /skills manager with audit and owned mutations

[SamhandsomeLee]

Summary

Delivers the Skills lane tracked on the v0.9.1 completion board (#4650): one /skills manager for inventory, audit, install/import, update, remove, and trust across CodeWhale-owned and compatible roots.

Refs #4650 (board: Skills / #4651 checkbox).
Refs #4651 (original product contract; issue was closed after load_skill listing mode — this PR completes the remaining manager / audit / mutation surface).

• Root catalog — single precedence/ownership source; only .codewhale/skills (project + global) is writable; .codex/skills is audit-only (not runtime).
• Bounded audit — unmerged inventory with Active / Shadowed / Duplicate / Conflict, package digests, provenance/trust classification, action policy; readiness stays Unknown until v0.9.1: Report artifact-skill readiness and define a managed dependency runtime #4407.
• Mutation controller — sole write path for Install / Import / Update / Remove / Trust; metadata + trust v2; TOCTOU digest checks; external roots never mutated.
• Skills Manager TUI — bare /skills opens owned-only, zero-network manager; view emits events only; host runs mutations and refreshes.
• Aliases — /skill install|update|uninstall|trust share the same controller; default install target is global owned.
• Docs/tests — docs/SKILLS.md, CONFIGURATION/GUIDE links; unit + skill_cli + Unix qa_pty coverage.

Commits

1. refactor(skills): centralize root catalog and precedence
2. feat(skills): add bounded audit inventory and status model
3. feat(skills): unify validated mutations and managed metadata
4. feat(tui): add unified skills manager view
5. test(skills): cover roots conflicts mutations and pty behavior
6. docs(skills): document manager audit provenance and readiness

Test plan

• cargo test -p codewhale-tui --bin codewhale-tui --locked skills::roots skills::audit skills::mutation skills_manager
• cargo test -p codewhale-tui --test skill_cli --locked
• cargo test -p codewhale-tui --test qa_pty --locked skills_opens_manager -- --test-threads=1 (Unix)
• Manual: bare /skills opens manager (no registry); c shows compatible; Esc closes
• Manual: import external → owned; remove/trust managed only; sentinel under .claude/skills untouched
• Manual: dual project+global same name requires --project / --global
• Confirm docs in docs/SKILLS.md match shipped behavior

Out of scope

• /skills audit CLI subcommand (manager + /skills inspect cover the need)
• v0.9.1: Report artifact-skill readiness and define a managed dependency runtime #4407 readiness probes (surface stays Unknown)
• Semantic skill comparison / second mutation stack / mutating harness roots

[github-actions]

Thanks @SamhandsomeLee for taking the time to contribute.

This repository is observing a maintainer-managed PR intake gate in dry-run mode, so this pull request is staying open. This note helps maintainers prepare the allowlist before any enforcement is considered.

Please read CONTRIBUTING.md for the expected contribution shape. A maintainer can grant recurring PR access by commenting /lgtm on a pull request.

[SamhandsomeLee]

@claude please code review