Open a sprite's texture or shader from the menus and inspector (#221)

A sprite's texture and shader were only reachable by hunting for them
in the asset panel. Every place that shows such a reference now leads
straight to it.

- Object menu (hierarchy and scene view): "Open texture" and "Open
  shader" sit right below "Open asset" when the sprite has one. The
  object's own values count, so an overridden shader opens the
  override.
- Asset context menu: the same entries at the top.
- Inspector: every asset field with a value shows its label as a blue,
  underlined link. One click selects the asset, a double click opens
  it. An override stays gold and gets the underline too.
- The first click rebuilds the inspector, so the second one lands on a
  different row. The inspector catches that second click before any
  row sees it.
- New pure rule `references.ts`: the asset behind a reference field. A
  frame leads to its sheet. Kinds without a tab (palette, font, sound)
  get no menu entry.
- `followsPress` in `clicks.ts` keeps the double-click window and
  tolerance in one place.
- `activateAsset` in `actions.ts`: opening means the same everywhere
  as a double click in the asset panel, so a scene also becomes the
  active one. The asset panel uses it too.

Tests:
- ./check.sh: 150 files, 2226 tests, CHECK EXIT 0 (before 148/2214).
- 12 new unit tests: 6 for the reference rule, 4 for the link in
  createFieldRow, 2 for followsPress.
- 5 new e2e checks in 28l-ii: both menus, the link's look, click
  selects, double click opens.
- e2e 1-16,26,28,35,39,40 on the final build: ALL PASSED, 732 checks.
- Counter-probes: no "Open ..." entries, no underline and a second
  click never recognised each fail exactly at their checks.
- Check total 1341 (CI counted 1336 at fd6af84), computed.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/editor/objectMenu.ts

@@ -2,9 +2,14 @@ import { UnpackContainerCommand } from '../core/commands/containerCommands';
 import { SetParentCommand } from '../core/commands/sceneObjectCommands';
 import { findObject } from '../core/model/hierarchy';
 import { isLiveInstance, isTemplateContent } from '../core/model/instance';
+import type { PropertyBag } from '../core/model/Properties';
 import { findAsset, type ObjectHolder } from '../core/model/Project';
+import { type PropertyDef, schemaForObject } from '../core/properties/PropertySchema';
+import { referencesOf } from '../core/properties/references';
+import { resolveSceneObjectProps } from '../core/properties/resolve';
 import { Menu, type MenuItem } from '../ui';
 import {
+  activateAsset,
   addCollider,
   addRigidbody,
   canAddCollider,
@@ -51,6 +56,13 @@ export function openObjectMenu(
       disabled: !asset || !hasAssetEditor(asset.type),
       onSelect: () => object && state.openAsset(object.assetId),
     },
+    ...(object && asset
+      ? openReferenceItems(
+          state,
+          schemaForObject(state.project, asset, object),
+          resolveSceneObjectProps(state.project, asset, object),
+        )
+      : []),
     {
       label: 'Add collider',
       disabled: !object || many || !canAddCollider(state.project, source, object),
@@ -89,3 +101,24 @@ export function openObjectMenu(
   menu.open(x, y);
   return menu;
 }
+
+/**
+ * "Open texture", "Open shader", … – one entry per asset the values point at (#221), skipping kinds
+ * that have no tab to open. The asset panel offers the same for an asset's own values.
+ */
+export function openReferenceItems(
+  state: EditorState,
+  schema: readonly PropertyDef[],
+  values: PropertyBag,
+): MenuItem[] {
+  return referencesOf(state.project, schema, values).flatMap(({ label, assetId }) => {
+    const target = findAsset(state.project, assetId);
+    if (!target || !hasAssetEditor(target.type)) return [];
+    return [
+      {
+        label: `Open ${label.charAt(0).toLowerCase()}${label.slice(1)}`,
+        onSelect: () => activateAsset(state, assetId),
+      },
+    ];
+  });
+}