Math delimiter trigger authority

Question

What should Plate treat as the authority stack for $...$ and $$...$$ typing-trigger behavior?

Current answer

This is no longer one clean winner row. It is at least three sub-surfaces:

• $ selection-wrap over selected text
• $ pair-on-type at an empty insertion point
• $$ block-math detection or promotion

Current evidence is:

• strong for Typora:
  • $ auto-pair when inline math is enabled
  • $$ + Return to enter block math
• strong for Milkdown:
  • inline math input rule for $...$
  • block math input rule for $$ trigger behavior
• strong for Obsidian:
  • math syntax docs exist for $...$ and $$
  • pair settings exist for markdown syntax
  • $ is explicitly in the markdown auto-pair family
  • $ selection-wrap is explicitly documented in release history
  • block $$ detection in-editor and block preview in Live Preview are both explicitly documented
• absent in current Plate runtime:
  • explicit insert APIs exist
  • current autoformat rules do not implement $ / $$ triggers

Why this matters

Without this gap being explicit, it is too easy to confuse:

• parser support for math delimiters
• explicit insert transforms
• selection-wrap input assist
• pair-on-type input assist
• block detection or promotion input assist

Those are not the same surface.

Current product answer

Plate's default rich-mode answer is now explicit:

• ship explicit-closing $...$ conversion
• ship $$ + Enter block promotion
• do not ship empty-selection opening-delimiter pair-on-type by default
• do not ship $ selection-wrap by default

Reason:

• $ and $$ already share the same symbol family in the rich editor
• adding default $ selection-wrap increases trigger ambiguity and collision pressure
• the Obsidian-style conservative selection-wrap branch is still valid evidence, but it fits better as a markdown/source-first profile decision than as the default rich-editor contract