Keep a pixel frame worn through a shader alive while it is drawn

Changing a palette colour of pixel art flooded the console with Pixi
warnings: "[BindGroup] a 'textureSource' was destroyed while still
bound to a shader", and the same for its sampler. #293 had stopped
this for a drawing, but a frame of pixel art is worn as a cut of the
sheet. The cut has a source of its own, so the sheet looked unbound,
was freed at once and took the cut with it under the shader.

- The check whether a replaced picture is still in use gets its key
  too. TextureLibrary then asks the picture and every cut taken from
  it.
- A sheet with a bound cut waits like a bound picture did since #293,
  and both go together once the shader has taken the new frame.

Found on the way:

- The project the report came from has a sprite wearing a frame of
  an eleven-frame pixel art through a shader asset.
- A nine-sliced sprite wearing the frame showed no warning, even
  without the change. The first try of the e2e check used it.

Tests:
- Gate on melektaus-atx: 236 files, 3577 tests (+1)
- e2e 48: 45 checks (+1, sum 1741). 48l-iii puts a shader on the
  object wearing the second frame, changes a palette colour three
  times and counts the warnings.
- Counter-checks bite: without the cuts in the check the unit test
  fails, and 48l-iii counts 6 warnings for 3 changes.

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

src/viewport/TextureLibrary.ts

@@ -36,7 +36,9 @@ export class TextureLibrary extends FileLibrary<Texture> {
       this.dropCropsOf(key);
       texture.destroy(true);
     },
-    boundToShader,
+    // A frame of pixel art is worn as a cut, which has a source of its own: the sheet itself is
+    // then bound nowhere, and freeing it destroyed the cut under the shader.
+    (texture, key) => boundToShader(texture) || this.cropsOf(key).some(boundToShader),
     // After the redraw that asked: every mesh it synced wears the new picture by then.
     (retry) => queueMicrotask(retry),
   );
@@ -152,7 +154,12 @@ export class TextureLibrary extends FileLibrary<Texture> {
     return Assets.load<Texture>(url);
   }
 
-  /** Cuts taken from a picture that has moved on to a newer revision; the key is their prefix. */
+  /** The cuts taken from one picture; the file is the prefix of their key. */
+  private cropsOf(file: string): Texture[] {
+    return [...this.crops].filter(([key]) => key.startsWith(`${file}|`)).map(([, texture]) => texture);
+  }
+
+  /** Cuts taken from a picture that has moved on to a newer revision. */
   private dropCropsOf(file: string): void {
     for (const [key, texture] of this.crops)
       if (key.startsWith(`${file}|`)) {

src/viewport/generatedPictures.ts

@@ -34,7 +34,7 @@ export class GeneratedPictures<T> {
    */
   constructor(
     private readonly free: (picture: T, key: string) => void,
-    private readonly inUse: (picture: T) => boolean = () => false,
+    private readonly inUse: (picture: T, key: string) => boolean = () => false,
     private readonly soon: (retry: () => void) => void = () => {},
   ) {}
 
@@ -80,7 +80,7 @@ export class GeneratedPictures<T> {
 
   private freeWaiting(): void {
     this.waiting = this.waiting.filter((held) => {
-      if (this.inUse(held.picture)) return true;
+      if (this.inUse(held.picture, held.key)) return true;
       this.free(held.picture, held.key);
       return false;
     });
@@ -95,7 +95,7 @@ export class GeneratedPictures<T> {
     const held = this.kept.get(key);
     if (!held) return;
     this.kept.delete(key);
-    if (!this.inUse(held.picture)) return this.free(held.picture, key);
+    if (!this.inUse(held.picture, key)) return this.free(held.picture, key);
     this.waiting.push({ key, picture: held.picture });
     if (this.asked) return;
     this.asked = true;