refactor(tests): centralize lane definitions and add per-file isolation

- extract test lane config to scripts/test-lanes.ts (single source of truth)
- run-test-lane.mjs: per-file bun process isolation with wall timeout; --jobs N, --single-process flags
- drop hand-listed test file lists from package.json; lanes now discovered by directory
- add test:stats (stats/src) and test:scripts (scripts/**) lanes; wire both into CI
- test:fast now: test:src + launcher-unit + test:scripts + test:runtime:compat
- remove obsolete test:full, test:core, test:core:dist, test:config:dist scripts

.github/workflows/prerelease.yml

@@ -70,6 +70,9 @@ jobs:
           path: coverage/test-src/lcov.info
           if-no-files-found: error
 
+      - name: Stats UI tests
+        run: bun run test:stats
+
       - name: Launcher smoke suite (source)
         run: bun run test:launcher:smoke:src