test: add dashboard frontend tests

[pilipilisbot]

Summary

• add Vitest + Testing Library for dashboard frontend tests
• cover query/path helpers, live status badge behavior, actor autocomplete, and session/transcript log grouping
• run dashboard npm test and npm run build in pull-request CI, plus release-time checks before publishing
• rebuild packaged dashboard static assets

Screenshots

No screenshots: this PR changes frontend test coverage/CI wiring, not dashboard UI behavior.

Validation

• cd dashboard && npm test
• cd dashboard && npm run lint
• cd dashboard && npm run build
• .venv/bin/python -m pytest -q
• git diff --check

Closes #45

[pilipilisbot]

Post-merge sync complete.

Summary:

• PR test: add dashboard frontend tests #46 merged into main at 88025bc.
• Post-merge GitHub Actions passed: tests run 26402325874 and release run 26402325935.
• Synced the canonical checkout to main at 88025bc and pruned the deleted origin/add-dashboard-frontend-tests ref.
• Removed the stale local add-dashboard-frontend-tests branch.
• No dedicated PR worktree existed; the canonical checkout is clean and was preserved.
• Latest published GitHub release is still v0.18.5; the release workflow completed without publishing a newer version for this test-only change.