feat(editor): preset-system polish — paint panel, slim action bar, icon rail (#354)

* feat(editor): preset-system polish — paint panel, slim action bar, icon rail

- Export `MaterialPaintPanel` so embedders host the paint material picker in
  their own panel (community docks it in the Build sidebar) instead of the
  bottom action bar.
- ActionMenu: drop the build / material-paint / furnish modes and the
  structure-tools palette row + paint tray (the host's Build sidebar owns
  building now). Reduce `structure-tools` to the shared `tools` lookup still
  used by cursor/floorplan indicators; remove the orphaned `useContextualTools`.
- MaterialPicker: swatches wrap into a fluid `auto-fill` grid that fills width.
- IconRail (tab-bar): bigger icons, grayscale-when-idle, Radix tooltip, w-14
  rail; sync `RAIL_WIDTH` to 56.
- Inspector footer: hand the host `footer` to kind-owned custom panels via
  `InspectorFooterContext` so the save button renders without per-kind wiring.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* chore: biome format pass

Whole-repo formatter normalization (line wrap/unwrap only, no logic changes)
surfaced by the format-on-edit hook against prior drift. Kept separate from the
feature commit so the preset-system diff stays reviewable.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

packages/nodes/src/column/definition.ts

@@ -154,20 +154,14 @@ function columnBraceHandle(axis: 'x' | 'z'): HandleDescriptor<ColumnNodeType> {
     axis,
     anchor: 'center',
     min: MIN_BRACE_DIMENSION,
-    currentValue: (n) =>
-      axis === 'x' ? (n.braceWidth ?? n.width) : (n.braceDepth ?? n.depth),
-    apply: (_n, newValue) =>
-      axis === 'x' ? { braceWidth: newValue } : { braceDepth: newValue },
+    currentValue: (n) => (axis === 'x' ? (n.braceWidth ?? n.width) : (n.braceDepth ?? n.depth)),
+    apply: (_n, newValue) => (axis === 'x' ? { braceWidth: newValue } : { braceDepth: newValue }),
     placement: {
       position: (n) => {
         // Position outside any splay so the arrow clears the legs.
         const half =
           axis === 'x'
-            ? Math.max(
-                n.braceBottomSpread ?? 0,
-                n.braceTopSpread ?? 0,
-                n.braceWidth ?? n.width,
-              ) / 2
+            ? Math.max(n.braceBottomSpread ?? 0, n.braceTopSpread ?? 0, n.braceWidth ?? n.width) / 2
             : (n.braceDepth ?? n.depth) / 2
         return axis === 'x'
           ? [half + BRACE_HANDLE_OFFSET, n.height / 2, 0]
@@ -205,12 +199,7 @@ function columnFootprintHalf(n: ColumnNodeType): { halfX: number; halfZ: number
   }
   return {
     halfX:
-      Math.max(
-        n.width,
-        n.braceWidth ?? 0,
-        n.braceBottomSpread ?? 0,
-        n.braceTopSpread ?? 0,
-      ) / 2,
+      Math.max(n.width, n.braceWidth ?? 0, n.braceBottomSpread ?? 0, n.braceTopSpread ?? 0) / 2,
     halfZ: Math.max(n.depth, n.braceDepth ?? 0) / 2,
   }
 }