test: [ENG-08] add verified TS coverage and paired performance reports

test/performance/README.md

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+# Paired performance and cleanup
+
+Run `yarn test:package` first. Set `ARTPLAYER_BROWSER_ARTIFACTS` to the resulting
+`refactor/.cache/packages/run-*/browser-artifacts.json`, then run
+`yarn test:performance`. The command starts its own local server; do not run it
+alongside other browser tests or CPU-heavy builds. All three engines run with one
+worker, no trace/video recording and the same media and viewport within a pair.
+
+Each engine runs three alternating published/candidate pairs. Each side retains
+one warm-up and five timed samples for both core and core + chapter, followed by
+separate instrumented resource probes. `scripts/performance-fixture.mjs` adapts
+only the frozen BASE-06 fixture's script URLs and report transport. Its original
+files remain unchanged and their existing baseline tests still run.
+
+The candidate must come from an isolated package installation. Artifact hashes,
+source snapshots, package inputs and build tools are checked before measurement;
+an old candidate cannot silently stand in for changed source. Raw, gzip 9 and
+Brotli 6 compare matching modern, legacy and ESM files from the same installation.
+Timing uses the exact JS files selected by the artifact map.
+
+Reports are in `refactor/.cache/performance/run-<engine>-*/report.json` and
+`summary.md`. Playwright evidence is in `refactor/.cache/performance/browser/`.
+CI uploads both and appends summaries to the workflow run. Failed or incomplete
+runs remain recorded and are not promoted to a passing baseline.
+
+A successful test proves the measurement contract and candidate resource cleanup.
+`review-required` means size or timing thresholds were exceeded; it is not release
+approval. CORE-22 and release reviews must resolve the corresponding risks before
+publishing. These counters do not measure native heap/GPU memory, real mobile
+hardware or screen-reader behavior. See `refactor/coverage-performance.md`.