feat(system-builder): CHARACTER SHEET page logic (4b3b)

[over2take]

frontend/src/sheets/sheetDesigner.ts: customize (copy the starter) and back to automatic; tabs added, renamed (refusing blank, long or repeated names), moved and removed (sections move to a chosen tab; the last tab makes a one-page sheet); sections and fields added, changed, moved and removed; the tray of starter fields not on a customized sheet; the header and max pairs forget fields that left; the name field stays; a formula's kind and editing are fixed; an attack number is never public. Every step is held to the server's checkDefinition in its tests.

statsRules.takenIds also counts a customized sheet's own fields, so a new stat or formula never takes one's id.

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