fix(windows-ci): curate Playwright-launching tests

Round 4 of windows-free-tests fixes. Round 3 cleared shard 2 except for
browse/test/batch.test.ts:35 which calls `await bm.launch()` and triggers
Playwright Chromium launch. The windows-latest runner doesn't have
Chromium installed (browser bring-up is a separate concern, tracked by
PR #1238 windows-pty-bun-pty-fix).

Fix: extend WINDOWS_FRAGILE_PATTERNS with `await \\w+\\.launch\\(` matcher.
Catches batch.test.ts plus 7 sibling tests (commands, compare-board,
content-security, handoff, security-live-playwright, security-sidepanel-dom,
snapshot — most already excluded by other patterns).

Curated Windows subset: 76 → 72 tests (~56% of free suite). Net curation
across all 4 rounds: 56 of 128 free tests excluded, each with a logged
reason. The 56 excluded fall into 6 buckets — POSIX shells, raw /tmp/,
chmod/xargs, file mode bitmasks, forward-slash path assertions, bin/
shebang spawns, and Playwright launches — all tracked as a P4 follow-up
TODO for full Windows parity.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

scripts/test-free-shards.ts

@@ -68,6 +68,12 @@ const WINDOWS_FRAGILE_PATTERNS: Array<{ pattern: RegExp; reason: string }> = [
   // tries to execute the file directly via CreateProcess, which fails on the
   // shebang. Catches gstack-question-log.test.ts, gstack-paths.test.ts, etc.
   { pattern: /path\.join\([^)]*,\s*['"]bin['"]\s*[,)]/, reason: 'spawns bin/ shebang script (Windows CreateProcess does not parse shebangs)' },
+  // Tests that launch a real Playwright browser. The windows-free-tests CI job
+  // runs a curated subset that intentionally does NOT install Chromium —
+  // browser bring-up on Windows is a separate concern (see PR #1238). Tests
+  // matching `await foo.launch(` need Chromium and fail with "Executable
+  // doesn't exist" on the runner.
+  { pattern: /await\s+\w+\.launch\(/, reason: 'launches Playwright browser (Chromium not installed in windows-free CI)' },
 ];
 
 export const DEFAULT_SHARD_COUNT = 20;