test: Added sandboxed, isolated Chromium first-run coverage with stat...

- package.json
- package-lock.json
- .gitignore
- playwright.config.ts
- e2e/fixtures.ts
- e2e/smoke.spec.ts
- tests/svg-image.test.tsx

GSD context:
- Milestone: M001 - Merge upstream v0.4.0 into the Gitea fork
- Slice: S02 - Verify combined application behavior
- Task: T01 - Added sandboxed, isolated Chromium first-run coverage with stateful synthetic API fixtures and fail-closed network boundaries.

GSD-Task: S02/T01

.gitignore

@@ -21,6 +21,11 @@ xai-credentials.json*
 # dev-fresh launcher scratch (fresh-user sim): disposable per launch
 .fresh-data/
 
+# Playwright: synthetic runtime data and failure diagnostics (never fixtures)
+.playwright-data/
+test-results/
+playwright-report/
+
 # ── GSD baseline (auto-generated) ──
 .gsd
 .gsd-worktrees/