benchmark-regression-triage

# Benchmark Regression Triage ## Overview This is a repo-local maintainer skill for VibeGuard contributors. It is intentionally stored under `.claude/skills/` so maintainers can use it while working in this repository, but it is not an installable product skill and must not be added to `schemas/install-modules.json` unless it is promoted into `skills/` or `workflows/` with a user-facing support contract. This skill diagnoses VibeGuard hook latency regressions by comparing GitHub Actions `bench-output` artifacts across PR runs, merge runs, and mainline runs. It is meant for non-obvious cases where the current benchmark is under budget but slower than a previous design, such as a `post-write-guard` path losing its `post-write-fast-check` fast path after a runtime migration. Treat CI artifacts as the trend source. Local benchmarks are useful for reproduction after a hypothesis exists, but they are not comparable to GitHub runner history because machine load, shell startup, cache state, and `--runs` count can dominate P95. ## When to Activate - A user asks why VibeGuard benchmark numbers are slower than before. - A PR appears to change hook latency, benchmark output, or benchmark-action reporting. - You need to compare recent PRs with older anchors such as PR #350 or a known fast-path implementation. - A hook is still below the absolute latency budget but may have lost a faster design. - You need a reusable workflow for downloading and comparing GitHub Actions `bench-output...