fix(skills): background review fork respects pinned skills

[teknium1]

Summary

The background self-improvement review fork now respects pinned skills, matching the curator. Previously a user-pinned skill could still be edited by the autonomous review fork — the guard only blocked external / bundled / hub-installed / protected-builtin skills, not pinned agent-owned ones.

Root cause: _background_review_write_guard in tools/skill_manager_tool.py checked ownership classes but never the pin flag. The curator skips pinned skills from every auto-transition; the review fork is the same kind of no-user-present actor and should too. This was the second concrete ask in #25839 (the first — stop forging role: "user" for review prompts — was already addressed: the review prompt is the fork's own user turn, gated by a memory/skills-only tool whitelist plus write-origin provenance).

Changes

• tools/skill_manager_tool.py: add a pin check to _background_review_write_guard, so background-origin edit/patch/delete/write_file/remove_file on a pinned skill are refused. Deliberately stricter than the foreground _pinned_guard (which only blocks delete) — with no user in the loop there is no one to consent to an edit.
• tests/tools/test_skill_manager_tool.py: background-review patch on a pinned skill is refused; an unpinned skill is NOT over-blocked.

Validation

Origin	Skill	Action	Result
background_review	pinned	patch/edit	refused
background_review	unpinned	patch	allowed
foreground	pinned	patch/edit	allowed (unchanged)
foreground	pinned	delete	refused (unchanged)

scripts/run_tests.sh tests/tools/test_skill_manager_tool.py tests/tools/test_skill_provenance.py → 103/103 passing.

Scope note: this addresses the pin-respect gap. The broader "gate all background-review skill writes behind approval" lever already exists as opt-in (skills.write_approval, default off) — left as-is since flipping that default is a separate product decision.

Reported by @xlionjuan (via their agent Kuri) in #25839.

Fixes #25839

Infographic

[github-actions]

🔎 Lint report: fix/review-fork-respect-pin-25839 vs origin/main

ruff

Total: 0 on HEAD, 0 on base (➖ 0)

🆕 New issues: none

✅ Fixed issues: none

Unchanged: 0 pre-existing issues carried over.

ty (type checker)

Total: 11491 on HEAD, 11493 on base (✅ -2)

🆕 New issues (1):

Rule	Count
invalid-assignment	1

First entries

tests/run_agent/test_credits_notices_toggle.py:76: [invalid-assignment] invalid-assignment: Object of type `None` is not assignable to attribute `_credits_session_start_micros` of type `int`

✅ Fixed issues (2):

Rule	Count
unresolved-attribute	2

First entries

run_agent.py:3002: [unresolved-attribute] unresolved-attribute: Object of type `Self@get_credits_spent_micros` has no attribute `_credits_session_start_micros`
tests/run_agent/test_credits_notices_toggle.py:76: [unresolved-attribute] unresolved-attribute: Unresolved attribute `_credits_session_start_micros` on type `AIAgent`

Unchanged: 6037 pre-existing issues carried over.

Diagnostics are surfaced as warnings — this check never fails the build.