optimize-looplisted

# optimize-loop Guessing is banned. Measure → find the real hot path → change ONLY it → prove the gain or revert. This skill sets the pipeline `planned` flag. ## Precondition Observability (§12) must exist — structured logs + spans/metrics on I/O boundaries and use cases. If it doesn't, STOP: you cannot optimize what you can't measure. Add instrumentation first (that's a build/maintain task), then return. ## Phases (state machine) 1. **baseline** (exit: numbers on record) — capture current metrics from observability/benchmarks: p50/p95/p99 latency, throughput, alloc/GC, db time, $ per op. Write them down. This is the bar. 2. **profile** (exit: bottleneck identified) — profiler/trace/flamegraph or span breakdown to find the REAL hot path. Amdahl: optimizing a 2% cost is wasted. Name the single dominant cost. 3. **hypothesize** (exit: ADR recorded) — state the expected gain AND the trade-off (memory, complexity, cache staleness, consistency) in an ADR. A perf change with no stated trade-off is suspicious. 4. **implement** (exit: change made) — ponytail + caveman; touch ONLY the hot path. Don't rewrite cold code for elegance. 5. **benchmark** (exit: gain proven) — re-measure the SAME way vs baseline. Real, repeatable gain beyond noise? keep. Marginal/none? **revert** — complexity without payoff is a loss. 6. **verify / commit / memory** — as BUILD. Verify includes correctness didn't regress (the fast wrong answer is still wrong). ## Rules - One