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/core/commands/assetCommands.ts

@@ -110,22 +110,24 @@ export function buildTextureAsset(name: string, image: TextureImage, id = newId(
 }
 
 /**
- * The image is uploaded before the command runs; this only records the result, so undo and redo
+ * The file is uploaded before the command runs; this only records the result, so undo and redo
  * never touch the network.
  */
-export class CreateTextureCommand implements Command {
+abstract class ImportFileCommand<A extends Asset & { file: string }> implements Command {
   readonly label: string;
-  readonly asset: TextureAsset;
 
-  constructor(name: string, image: TextureImage) {
-    this.asset = buildTextureAsset(name, image);
-    this.label = `Import texture "${name}"`;
+  constructor(
+    readonly asset: A,
+    private readonly fileNoun: string,
+    private readonly isStored: (file: string) => boolean,
+  ) {
+    this.label = `Import ${asset.type} "${asset.name}"`;
   }
 
   execute(project: Project): void {
     // The name is the hash the server derived from the bytes; anything else was never uploaded.
-    if (!isTextureFile(this.asset.file))
-      throw new CommandError(`"${this.asset.file}" is not a stored image file`);
+    if (!this.isStored(this.asset.file))
+      throw new CommandError(`"${this.asset.file}" is not a stored ${this.fileNoun} file`);
     project.assets.push(this.asset);
   }
 
@@ -134,28 +136,19 @@ export class CreateTextureCommand implements Command {
   }
 }
 
+export class CreateTextureCommand extends ImportFileCommand<TextureAsset> {
+  constructor(name: string, image: TextureImage) {
+    super(buildTextureAsset(name, image), 'image', isTextureFile);
+  }
+}
+
 export function buildFontAsset(name: string, file: string, id = newId()): FontAsset {
   return { id, name, props: defaultsFor('font'), type: 'font', file };
 }
 
-/** The typeface is uploaded before the command runs, as an image is for `CreateTextureCommand`. */
-export class CreateFontCommand implements Command {
-  readonly label: string;
-  readonly asset: FontAsset;
-
+export class CreateFontCommand extends ImportFileCommand<FontAsset> {
   constructor(name: string, file: string) {
-    this.asset = buildFontAsset(name, file);
-    this.label = `Import font "${name}"`;
-  }
-
-  execute(project: Project): void {
-    if (!isFontFile(this.asset.file))
-      throw new CommandError(`"${this.asset.file}" is not a stored font file`);
-    project.assets.push(this.asset);
-  }
-
-  undo(project: Project): void {
-    project.assets = removeById(project.assets, this.asset.id);
+    super(buildFontAsset(name, file), 'font', isFontFile);
   }
 }
 
@@ -163,24 +156,9 @@ export function buildSoundAsset(name: string, file: string, id = newId()): Sound
   return { id, name, props: defaultsFor('sound'), type: 'sound', file };
 }
 
-/** The sound is uploaded before the command runs, as a typeface is for `CreateFontCommand`. */
-export class CreateSoundCommand implements Command {
-  readonly label: string;
-  readonly asset: SoundAsset;
-
+export class CreateSoundCommand extends ImportFileCommand<SoundAsset> {
   constructor(name: string, file: string) {
-    this.asset = buildSoundAsset(name, file);
-    this.label = `Import sound "${name}"`;
-  }
-
-  execute(project: Project): void {
-    if (!isSoundFile(this.asset.file))
-      throw new CommandError(`"${this.asset.file}" is not a stored sound file`);
-    project.assets.push(this.asset);
-  }
-
-  undo(project: Project): void {
-    project.assets = removeById(project.assets, this.asset.id);
+    super(buildSoundAsset(name, file), 'sound', isSoundFile);
   }
 }