feat: add device position undo history

Issue: #74
User-Visible: yes

scripts/coordinate-write-barrier-guard.mjs

@@ -44,7 +44,7 @@ export function checkCoordinateWriteBarriers(root = defaultRoot) {
   }
 
   const positionWrites = occurrences(frontend, "type: 'houseplan/layout/update'");
-  if (positionWrites.length !== 2) errors.push(`frontend position writer inventory: ${positionWrites.length}`);
+  if (positionWrites.length !== 3) errors.push(`frontend position writer inventory: ${positionWrites.length}`);
   for (const [ordinal, index] of positionWrites.entries()) requireWindow(
     errors, frontend, index,
     /const pos = canonicalizePosition\([^)]+\);[\s\S]*pos(?:[,\s}])/,

scripts/mutation-gate.mjs

@@ -2282,6 +2282,17 @@ const MUTANT_DEFINITIONS = [
       replace: '  const exact = false ? exactCoveringWall(walls, a, b, pitch, coordScale) : null;',
     }],
   },
+  {
+    id: 'device-position-cancel-routed-to-commit',
+    guard: 'node demo/smoke_device_position_history.mjs',
+    because: 'pointer cancellation and lost capture must restore the uncommitted device preview '
+      + 'without creating a position command or writing layout (#74)',
+    patches: [{
+      file: 'src/houseplan-card.ts',
+      find: '@pointercancel=${(e: PointerEvent) => this._pointerCancel(e, d)}',
+      replace: '@pointercancel=${(e: PointerEvent) => this._pointerUp(e, d)}',
+    }],
+  },
   {
     id: 'stale-space-position-guard-removed',
     guard: 'npx tsc -p tsconfig.test.json && node scripts/fix-test-build.mjs '
@@ -2290,8 +2301,8 @@ const MUTANT_DEFINITIONS = [
       + 'and websocket side effects when that space has been deleted or renamed',
     patches: [{
       file: 'src/houseplan-card.ts',
-      find: '    if (!this._spaceModelById(d.space)) return;\n    if (this._norm) {',
-      replace: '    if (this._norm) {',
+      find: '    if (!this._spaceModelById(d.space)) return;\n    this._layout = applyDevicePlacement(',
+      replace: '    this._layout = applyDevicePlacement(',
     }],
   },
   {

scripts/smoke-links.mjs

@@ -27,6 +27,17 @@
 
 /** @type {SmokeLink[]} */
 export const SMOKE_LINKS = [
+  {
+    symbols: [
+      'applyDevicePlacement', 'devicePlacement', 'sameDevicePlacement',
+      'DevicePlacement', 'DevicePositionState',
+    ],
+    smokes: ['smoke_device_position_history.mjs'],
+    because: 'the #74 production-bundle scenario drives real Device editor pointer events and '
+      + 'observes transaction boundaries, point-wise update/delete, toolbar history, native field '
+      + 'shortcuts, cancellation and revision invalidation; none of those browser effects can be '
+      + 'proved by the pure placement helpers alone',
+  },
   {
     symbols: [
       'resolveValueSource', 'valueSourceWriteFields', 'valueBadgeCandidates',