Use uv run pytest for uv-managed projects

[benthomasson]

Problem

--run-tests runs bare pytest, which fails in uv-managed projects where pytest is only available via uv run pytest. The review reports:

Running pytest on related test files...
Tests: 0 passed, 0 failed, 0 errors (0.02s) — ERROR

The system Python doesn't have pytest installed — it's a dev dependency managed by uv in the project's virtualenv.

Proposed Fix

Detect uv-managed projects (e.g., check for pyproject.toml with [tool.uv] or a .venv created by uv) and use uv run pytest instead of bare pytest. Fallback chain:

1. uv run pytest (if uv project detected)
2. pytest (current behavior)

Context

Discovered while reviewing benthomasson/ftl-sdlc-loop#10 — all 48 tests pass with uv run pytest but code-review review-loop --run-tests reports ERROR.