feat(editor): node-declared per-context snapping + contextual HUD + painter scope

Generify the snapping/modifier HUD off the FSM scope and node declarations
instead of wall-creation-shaped, leaking pills.

- Per-context snapping (`snappingModeByContext`, persisted): wall / item /
  polygon mode-sets with exclusive modes (grid | lines | angles | off), each
  doing exactly what its chip says. Context is node-declared via the new
  `NodeDefinition.snapProfile` ('item' | 'structural'); the resolver maps
  (profile × action) → context with no per-kind switch.
- Scope-driven HUD: helper-manager reads the interaction scope; reshaping
  (endpoint/curve/boundary) and item move get their own chip, no select-hint
  leak. Rotate R/T rounds to 45°; Alt = force-place only (hidden for
  structural kinds); Shift = cycle everywhere.
- Slab/ceiling drafting: Shift=cycle, mode-aware grid/angle, Enter finishes
  (minDraftVertices); polygon boundary vertex/edge drag begins a reshaping
  scope. Fix grid/angle being ignored on boundary edit + slab creation:
  make resolveSurfacePlanPointSnap exclusive (alignment gated on magnetic) so
  grid/angles keep the snapped fallback instead of the raw cursor.
- Painter application scope: node-derived (single/object/matching/room) from
  the hovered node, cyclable via Shift, single-source HUD chip.
- Remove the redundant GridSnapControl from view-toggles (grid step lives in
  the contextual HUD now).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

packages/nodes/src/fence/actions/move-endpoint.ts

@@ -11,6 +11,7 @@ import {
 } from '@pascal-app/core'
 import {
   type FencePlanPoint,
+  isAngleSnapActive,
   isMagneticSnapActive,
   isSegmentLongEnough,
   snapFenceDraftPoint,
@@ -164,15 +165,18 @@ export const moveFenceEndpointDragAction: DragAction<MoveFenceEndpointCtx, MoveF
 
     preview: (ctx, point, modifiers) => {
       const planPoint: FencePlanPoint = [point[0], point[1]]
-      // Endpoint move = grid snap only; the 45°-from-start angle snap
-      // is draft-only. Shift is a hard snap bypass.
+      // Endpoint move honours the active snapping mode (HUD chip): grid → lattice;
+      // lines → magnetic corner/alignment; angles → lock to 15° rays from the
+      // fixed corner; off → raw. No Shift bypass — Shift cycles the mode; Off is
+      // the bypass.
       const snapped = snapFenceDraftPoint({
         point: planPoint,
         walls: ctx.levelWalls,
         fences: ctx.levelFences,
         ignoreFenceIds: [ctx.fenceId as string],
-        bypassSnap: modifiers.shift,
-        magnetic: !modifiers.shift && isMagneticSnapActive(),
+        start: ctx.fixedPoint,
+        angleSnap: isAngleSnapActive(),
+        magnetic: isMagneticSnapActive(),
       })
 
       // Figma-style alignment: nudge the dragged endpoint onto another wall /
@@ -180,7 +184,7 @@ export const moveFenceEndpointDragAction: DragAction<MoveFenceEndpointCtx, MoveF
       // guide. The resolver connects to the NEAREST real anchor, so the dot
       // always sits on an actual point. Alt is reserved for detach.
       let aligned = snapped
-      if (!modifiers.shift && ctx.alignCandidates.length > 0) {
+      if (isMagneticSnapActive() && ctx.alignCandidates.length > 0) {
         const ar = resolveAlignment({
           moving: [{ nodeId: ctx.fenceId as string, kind: 'corner', x: snapped[0], z: snapped[1] }],
           candidates: ctx.alignCandidates,