feat(system-builder): the builder's saving and sidebar, as logic (4a2a)

[over2take]

sheets/builderSession.ts: createAutosave (saves the latest edit 5s after editing stops; flush saves now and keeps going until nothing is unsaved; an edit made during a save is kept and saved after it; never two saves at once; a failed save keeps the edit and is retried), the status line (DRAFT · SAVED 14:02 / UNSAVED CHANGES / SAVING… / NOT SAVED: why), the exit warning used only when the save on leaving failed, leaveNeedsAsking for the browser tab, publishBlocked / publishedMessage, and BUILDER_PAGES with a line each.

systemsApi gains saveDraft and publish, and get's full answer type.

The publish route now emits customSystemChanged, so open browsers fetch the new version.

Decided with the user 2026-10-06: two save layers (autosave writes the draft; SAVE saves now; PUBLISH goes live); EXIT TO MAP warns only when a save failed.

Summary

Test plan

• Tested locally
• Tests pass

Pre-merge checklist

Code quality:

• Code follows project style
• No breaking changes (or clearly documented)
• No console errors or warnings

Version & Release:

• Version bumped? If releasing to users, update:
  • frontend/package.json version
  • docker-compose.yml APP_VERSION
  • CHANGELOG.md with release notes
• GitHub Actions will auto-tag Docker images with the new version

Before merging to main:

• All tests passing
• PR reviewed and approved
• Branch is up to date with main
• No merge conflicts

Related issues