Asset panel: double-click opens the tab, single click only selects (#71)

One rule for every asset type: a click on an asset row selects it, a
double-click (or Enter, or creating it via +) opens its tab. Selection
alone still switches tabs only for nodes, frames and template objects.

- state.openAsset(id) = select + 'open' event; the editor maps the asset
  type to its tab via TAB_OF_ASSET. The two special clauses for state
  machine and shader assets in the selection handler are gone.
- Creating via + and importing a texture from the picker open the tab;
  paste/drop of an image only selects.
- 3 unit tests (event order, re-open of a selected asset, selection never
  fires open), 14 e2e checks in step 4.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/editor/textureImport.ts

@@ -156,7 +156,9 @@ function adopt(
  */
 export function importStoredImage(image: UploadedTexture, deps: TextureImportDeps): ImportOutcome {
   const outcome = adopt(image, 'Texture', image.file, deps);
-  selectLast([outcome], deps);
+  // Chosen in the picker, so this is "+ → Texture": the tab opens like for any created asset. A
+  // pasted or dropped picture (`importImages`) only selects – it usually goes into the scene.
+  if (outcome.assetId) deps.state.openAsset(outcome.assetId);
   deps.state.setNotice(
     outcome.error ??
       (outcome.reused ? 'That image is already in the project.' : 'Added the image to the project.'),