Treat bundled cleanup hooks as built-ins

[copyberry]

Treat bundled cleanup hooks as built-ins

What changed

• Centralize the allowlist for bundled MCP cleanup hooks and use it for both local and executor-discovered plugins, including unified-computer-use cleanup through cua_repl.
• Mark matching cleanup hooks as trusted built-ins so they run without saved hook trust and remain active when regular hooks or their per-hook state are disabled. Plugin enablement and managed-only policy still apply.
• Hide built-in cleanup hooks from hook listings and lifecycle notifications while retaining their metrics. Keep the built-in classification out of serialized protocol data.

Testing

• Cover allowlist boundaries, trust and enablement behavior, inline and file-based hook declarations, MCP success and error responses, hook listing, lifecycle notifications, metrics, and protocol serialization.