Edge/corner stretch — done

Stretching an edge or corner had three stacked bugs.

Wrong edge picked near corners. test_edges returned the first edge within proximity radius — index order won the tiebreak. Fixed: track minimum distance, return closest.

Both edges flew apart. Changing one bound shifts center by Δ/2. Through rotation, that center shift moves every vertex in world space. Opposite edge drifts. Fix: pin opposite-side vertex. Capture its world position at mousedown, recompute after bound change, adjust scene.position to cancel the drift. Drift goes through inverse parent world matrix — position lives in parent space, not world.

Accumulation noise on a moving plane. Old code used frame-to-frame deltas on a plane that shifted as bounds changed. Replaced with the stretch anchor pattern: freeze face geometry at mousedown, compute absolute offsets from snapshot every frame. Same pattern as face translation.

Stretch anchor pattern

1. Mousedown — capture face plane geometry (e1/e2 world+local, plane point, normal, anchor world pos). Snapshot affected bounds + position + opposite vertex.
2. Every frame — intersect current mouse with the fixed plane. Absolute world delta from anchor. Decompose onto frozen e1/e2. Map to local via frozen e1_local/e2_local. Dot with axis vector(s) → absolute bound offset(s).
3. Apply — reset bounds and position to initial, apply offsets, compensate center-rotate-uncenter shift by pinning opposite vertex.

Click-to-select — done

Two event systems both handled mousedown on the 3D canvas. Events_3D (canvas listener) used canvas-relative coords and selected the right face. Then the event bubbled to Events.ts (document listener) → Hits.ts, which re-ran hit_test with page coordinates — wrong coordinate space — and overwrote the selection with the root SO.

Fix in Hits.ts: the 3D fallback path now bails on mouseup (!s_mouse.isDown) and on mousedown if Events_3D already set a drag target (drag.has_target). Also moved Events_3D mouseup from window to document so both systems listen at the same level.