test(make): forbid bare 'uv run' in review-safe gates (#2296)

[yastman]

This pull request was created by @kiro-agent on behalf of @yastman 👻

Comment with /kiro fix to address specific feedback or /kiro all to address everything.
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Summary

Closes #2296 — guards the read-only review/candidate validation gates against silently regressing to a mutating uv run.

Background

make check (via lint / type-check) uses plain uv run, which auto-syncs the shared project .venv. In review/candidate worktrees this re-points the editable install at the temporary worktree and can switch package versions — the exact footgun observed during PR-queue validation (a later make candidate-check then failed as stale). #2290 added check-frozen / candidate-check (preflight uv sync --frozen --check + run tools via $(UV_RUN_NO_SYNC)), but nothing guarded that read-only guarantee against future regression.

Fix

Per the issue's proposed option, add a Makefile contract test (tests/contract/test_makefile_review_gate_no_autosync_contract.py) asserting:

• check-frozen and candidate-check exist;
• check-frozen preflights read-only with uv sync --frozen --check;
• every uv run inside the review-safe gates uses --no-sync (directly or via $(UV_RUN_NO_SYNC)) — never a bare auto-syncing uv run;
• check-frozen covers both ruff check and mypy via the no-sync runner;
• the $(UV_RUN_NO_SYNC) macro itself resolves to --no-sync.

Developer-friendly make check is intentionally not constrained (auto-sync there is fine, per the issue). Detector self-checks pin the helper so the contract can't go vacuous.

Testing (TDD — verified red first)

• Injecting a bare uv run into check-frozen makes test_review_safe_gates_never_use_bare_uv_run fail with the offending line; restored → green.
• pytest tests/contract/ -k makefile → 61 passed. Ruff clean.
• No production code changed (test-only; the Makefile already satisfies the contract thanks to fix: read-only candidate-check and bot no-sync for stale venv safety #2290).

verify:repo-only — no Docker/runtime validation required.