Math Trigger Execution

Goal

Implement the first safe rich-mode math trigger slice directly.

Scope

• no selection-wrap shipping by default
• no opening-delimiter pair-on-type for $
• allow explicit-completion rich-mode conversion
• implement $$ + Enter block promotion

Planned Slice

1. shared math trigger plugin in @platejs/math
2. inline conversion on completed $...$ only
3. block conversion on $$ then Enter
4. math kit wiring
5. package + app integration tests
6. docs/law updates so shipped rows match runtime truth

Verification

• targeted bun test
• pnpm brl
• build before typecheck
• pnpm lint:fix
• browser check if docs/demo surface changed

Progress

• [done] Added shared rich-mode math trigger infrastructure in @platejs/math.
• [done] Shipped the safe slice:
  • completed $...$ converts inline on closing delimiter
  • $$ + Enter promotes block math
• [done] Kept selection-wrap deferred by default.
• [done] Wired the trigger plugin into BaseMathKit and MathKit.
• [done] Added package and app integration coverage.
• [done] Updated docs and editor-behavior law to match the shipped slice.