Two compilers that walk a graph the same way walk it through one emitter (#85)

Refactoring round two: the particle and shader compilers share emitGraph.ts (cycle detection,
duplicate names, emit order) and keep only their rules. FontLibrary and TextureLibrary sit on
FileLibrary (base URL, loading/failed bookkeeping, listeners); SoundLibrary keeps its own
contract. The three Create*Command share ImportFileCommand, the three renames share
RenameCommand - class names stay. bandBounds() in framing.ts and portNameField() in
portSection.ts replace in-file clones, and three comments that told history now state the rule.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/viewport/TextureLibrary.ts

@@ -1,8 +1,7 @@
 import { Assets, CanvasSource, Texture } from 'pixi.js';
 import type { FrameRect, TextureRef } from '../core/model/texture';
 import { type EdgeMode, SHEET_EDGE } from '../core/shader/nodes';
-
-const DEFAULT_BASE = '/game-maker/data/textures';
+import { FileLibrary } from './FileLibrary';
 
 /**
  * Pixi turns `clamp-to-edge` into `repeat` on every texture a Graphics fill draws with
@@ -22,24 +21,14 @@ const ADDRESS_MODE: Record<EdgeMode, 'repeat' | 'mirror-repeat' | 'clamp-to-edge
   clamp: 'clamp-to-edge',
 };
 
-/**
- * Keeps uploaded images on the GPU, keyed by file name. Nothing is evicted: file names are
- * content addressed, so a cached texture can never go stale. A miss is not an error – it starts
- * the load and reports "not yet", so callers never await and get a redraw when the picture lands.
- */
-export class TextureLibrary {
-  private base = DEFAULT_BASE;
+/** Keeps uploaded images on the GPU; callers never await and get a redraw when the picture lands. */
+export class TextureLibrary extends FileLibrary<Texture> {
   private readonly loaded = new Map<string, Texture>();
   /** Frames cut from their sheets, keyed by file and rectangle; kept like the files. */
   private readonly crops = new Map<string, Texture>();
-  private readonly loading = new Set<string>();
-  /** Never retried, so one broken reference cannot spam the network. */
-  private readonly failed = new Set<string>();
-  private readonly listeners = new Set<() => void>();
 
-  /** Where the files are served from. Set once at start-up, before anything draws. */
-  configure(base: string): void {
-    this.base = base.replace(/\/+$/, '');
+  constructor() {
+    super('/game-maker/data/textures', 'textures');
   }
 
   /**
@@ -83,12 +72,6 @@ export class TextureLibrary {
     return this.loaded.get(file) ?? null;
   }
 
-  /** Runs `fn` whenever a picture has arrived; returns the unsubscribe. */
-  onChange(fn: () => void): () => void {
-    this.listeners.add(fn);
-    return () => this.listeners.delete(fn);
-  }
-
   /**
    * A frame as a texture of its own, cut the first time it is asked for. Drawn from the sheet
    * through a fill matrix it showed a row of the neighbouring cell along any edge that fell
@@ -110,23 +93,14 @@ export class TextureLibrary {
     return texture;
   }
 
-  private startLoading(file: string): void {
-    if (this.loading.has(file) || this.failed.has(file)) return;
-    this.loading.add(file);
-    void Assets.load<Texture>(`${this.base}/${file}`).then(
-      (texture) => {
-        this.loading.delete(file);
-        texture.source.style.addressMode = EDGE_MODE;
-        texture.source.style.update();
-        this.loaded.set(file, texture);
-        for (const listener of this.listeners) listener();
-      },
-      (error: unknown) => {
-        this.loading.delete(file);
-        this.failed.add(file);
-        console.error(`[textures] cannot load ${file}`, error);
-      },
-    );
+  protected fetchFile(url: string): Promise<Texture> {
+    return Assets.load<Texture>(url);
+  }
+
+  protected keep(file: string, texture: Texture): void {
+    texture.source.style.addressMode = EDGE_MODE;
+    texture.source.style.update();
+    this.loaded.set(file, texture);
   }
 }