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/portCommands.ts

@@ -19,7 +19,7 @@ import {
 import type { PropertyValue } from '../model/Properties';
 import type { Project } from '../model/Project';
 import { type Removed, removeFirst, removeWhere, restoreAt } from '../util/list';
-import { type Command, CommandError } from './Command';
+import { type Command, CommandError, RenameCommand } from './Command';
 import { nextFieldName } from './naming';
 import { requireBehavior, requireNode, requireNodeDef } from './require';
 
@@ -260,27 +260,17 @@ export class SetPortWriteCommand implements Command {
 }
 
 /** Rewrites the edges and inline values pointing at the port too, in every graph that has any. */
-export class RenamePortCommand implements Command {
-  readonly label: string;
-
+export class RenamePortCommand extends RenameCommand {
   constructor(
     private readonly assetId: string,
     private readonly nodeId: string,
-    private readonly from: string,
-    private readonly to: string,
+    from: string,
+    to: string,
   ) {
-    this.label = `Rename ${from}`;
+    super(`Rename ${from}`, from, to);
   }
 
-  execute(project: Project): void {
-    this.rename(project, this.from, this.to);
-  }
-
-  undo(project: Project): void {
-    this.rename(project, this.to, this.from);
-  }
-
-  private rename(project: Project, from: string, to: string): void {
+  protected rename(project: Project, from: string, to: string): void {
     if (from === to) return;
     const node = requireNode(project, this.assetId, this.nodeId);
     const sites = portSites(project, this.assetId, node);