test: repair serial-bucket quick wins and quarantine intractable specs (phase 4b)

Repairs (74 tests across 6 files):
- rbac.spec.ts, settings.spec.ts: fix obsolete auth-state path
  (test-results/.auth/user.json -> .playwright/.auth/user.json via
  authFile import from playwright.config.ts)
- state-bleed-audit.spec.ts, gui-file-carry.spec.ts, full-session.spec.ts:
  update bare tool routes (/resize -> /image/resize, etc.) to match the
  2.0 /:modality/:toolId routing
- gui-settings-rbac.spec.ts: fix 2 tests with bare /resize route

Quarantine (65 tests across 2 files, tagged with test.skip()):
- gui-performance.spec.ts (62 tests): bare routes throughout + selector
  drift; mechanical route fix is tractable but needs UI verification pass
- theme.spec.ts (3 tests): footer theme toggle selector needs 2.0 UI
  verification

QUARANTINE.md updated with full triage table. Vitest parity confirmed.

tests/e2e/gui-performance.spec.ts

@@ -1,5 +1,14 @@
 import { expect, openSettings, test, uploadTestImage } from "./helpers";
 
+// Phase 4b quarantine: 62 tests use bare tool routes (e.g. /resize instead of
+// /image/resize) that 404 on the 2.0 prod-build preview server. Mechanical
+// route fix is tractable but the file also has selector assumptions (fullscreen
+// grid, search bar, tool-list layout) that need 2.0 UI verification. Deferred
+// to Phase 4 tail.
+//
+// eslint-disable-next-line -- quarantine skip
+test.skip(true, "Phase 4b quarantine: bare tool routes + selector drift");
+
 // ---------------------------------------------------------------------------
 // GUI Performance: Page load budgets, SPA navigation, interaction responsiveness
 // ---------------------------------------------------------------------------