001: Fix Agent Cycle Time (7-21 min)

Problem

Fix agent takes 15-21 min per review-fix cycle. Telemetry shows ~70% is shell command execution (make test, make lint, git, gh api), only ~30% is LLM inference.

Data (PR #7)

Metric	Run A (~17 min)	Run B (~21 min)
LLM API time	284s (29%)	342s (29%)
Tool execution (shell)	690s (71%)	833s (70%)
Total tokens	1.49M (89% cached)	2.38M (91% cached)

Optimization Targets

1. Targeted testing — run only tests for changed packages instead of full make test
2. Pre-fetch PR context — fetch review comments in workflow step, not via LLM tool calls
3. Time budget — add timeout-minutes: 20 on the LLM step
4. Skip tests for non-code changes — workflow-only or markdown-only PRs don't need make test