refactor: simplify dashboard & limits logic, improve perf

- Rewrite web dashboard for leaner layout and better performance (src/web.ts +1041)
- Rework Codex auth flow with improved session handling (src/codex-auth.ts +264)
- Add usage failure classification (authInvalid, workspaceDeactivated,
  workspaceDeactivatedReason, shouldProbeFallback) in usage-limits
- Extend probe-limits and refresh-queue logic (+158 / +96)
- Add LoginAccountOptions with timeoutMs in auth
- Enhance auto-login Python script (+475 lines)
- Add unit tests for limits-refresh, refresh-queue, usage-limits
- Drop ops/release.mjs in favor of manual release flow
- Rebuild dist/

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>