feat(ui): streamline release workflow UX

[Armaldio]

Summary

• Keep the Configuration / Builds / Artifacts / Runs architecture and current best-default behavior.
• Standardize the Workflow header and section-heading hierarchy across all four tabs.
• Protect workflow edits during route navigation and browser close/reload, including in-flight/failed saves and unapplied Build settings.
• Add race-safe Source and producer inspection feedback, actionable Build issue routing, a provider-only Add destination picker, and deduplicated readiness summaries.
• Keep Build removal in settings, update the Release Workflows guide, remove the temporary root plan.md, and leave the Phase 5 changeset unchanged.

Screenshots

Configuration — light	Configuration — dark

Builds	Artifacts

Runs	Narrow Configuration view

New Release wizard — Review

Final audit status

• All PR feat(ui): streamline release workflow UX #110 audit findings resolved without expanding Phase 5 scope.
• Unsaved-state protection and the Phase 5 regression gate complete.

Verification

• pnpm --filter @pipelab/ui test: 94 tests passed.
• UI typecheck, lint (0 errors; 23 existing warnings), and build passed.
• Documentation build passed.
• Chromium with a mocked backend verified Build save-before-navigation, failed-save navigation blocking, staged-settings Keep editing / Discard changes, and beforeunload behavior for staged edits plus pending, in-flight, failed, and fully saved workflow states.
• Chromium also verified Configuration issue navigation, Source inspection reruns and recovery, Add destination selection, and narrow light/dark Build and Configuration views.
• GitHub Actions for 8223086d passed: CI (test, typecheck, lint, build), CodeQL, and documentation deployment.