fix(dashboard): UI polish — modals, layout, consistency, test fixes

Dashboard UX polish pass — consolidates create forms into modals
triggered from the page header, fixes layout inconsistencies, adds
scroll-to navigation for the Keys page, and aligns the TokenBar with
the design system.

Changes:
- App.tsx: add padding to sidebar header
- resolve-page-title.ts: add missing routes, better fallback title
- en.ts: fix nav labels (Profiles was 'profiles : multi agents')
- ModelsPage: two-col layout, auxiliary tasks modal, TokenBar redesign
- ProfilesPage: create button in header, form in modal, Checkbox component
- CronPage: create button in header, form in modal
- EnvPage: scroll-to sub-nav in header, fix text overflow

Modal and dialog standardization:
- Replace all native confirm()/window.confirm() with ConfirmDialog
  (OAuthProvidersCard, PluginsPage, ModelsPage, ConfigPage)
- Add useModalBehavior hook (Escape-to-close, scroll lock, focus restore)
- Apply hook to ProfilesPage, CronPage, AuxiliaryTasksModal

Component fixes (from PR review):
- Checkbox: fix controlled/uncontrolled mismatch, add focus-visible ring
- TokenBar: add rounded-full to legend dots, remove dead code

CI/test fixes:
- Fix TS unused imports (noUnusedLocals), type-narrow PickerTarget union
- Add windows-footgun suppression on platform-guarded os.killpg
- Fix 19 stale unit tests + 9 e2e tests broken by recent main changes
- Restore minimal example-dashboard plugin for plugin auth test

tests/test_ctx_halving_fix.py

@@ -169,6 +169,7 @@ class TestEphemeralMaxOutputTokens:
         agent.reasoning_config = None
         agent._is_anthropic_oauth = False
         agent._ephemeral_max_output_tokens = None
+        agent._use_long_lived_prefix_cache = False
 
         compressor = MagicMock()
         compressor.context_length = 200_000