Footnote Product Surface

Goal

Implement the missing footnote product surface end-to-end:

• tf.insert.footnote
• footnote helpers and navigation
• app/demo toolbar and slash-command entry points
• footnote rendering helpers needed for preview/backlink behavior
• docs/spec sync

Phases

• [in_progress] Audit current footnote package seams and clone the right insert/navigation patterns from adjacent packages
• [pending] Add red tests for package-level footnote insert and navigation behavior
• [pending] Implement footnote transforms, queries, and plugin API in @platejs/footnote
• [pending] Wire React/app UI surfaces: toolbar, slash, rendering/backlink/preview helpers
• [pending] Update docs/spec language to match the implemented package surface
• [pending] Run package/app verification and summarize the shipped contract

Constraints

• Use one coherent lane, not insert-only.
• Default to numeric identifiers and avoid duplicate definitions.
• Definition placement should be deterministic and sane.
• If Plate does not support a Typora-like surface yet, say so plainly.