Second Stage D affordance port (425 LoC legacy → ~430 split across
action + wrapper). All math (snap, linked-fence cascade, alt-detach,
min-length gate, single-undo dance) lives in the pure
`moveFenceEndpointDragAction`. The React wrapper handles the UI
overlays (cursor sphere, Drag/Detach badge, angle label) and the live
state subscriptions.
The action introduces the single-undo dance pattern for multi-write
commits: `commit()` calls `scene.restoreAll()` → `resumeHistory()` →
re-applies the final draft so zundo records the entire drag as one
undo step. Reusable shape for slab/wall/door endpoint ports.
Transitional exports added to `@pascal-app/editor`'s public surface
(`snapFenceDraftPoint`, `isWallLongEnough`, the segment-angle helpers,
`MovingFenceEndpoint`). Stage F cleanup moves these into
`@pascal-app/nodes` once every consumer is registry-driven.
`getRegistryAffordanceTool` is now generic (`ComponentType<any>`) so
affordances with different prop shapes (`{ node }`, `{ target }`, …)
all dispatch through the same helper.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
