refactor(runtime): compose consumers over fs and subprocess

packages/skill/skill-local/tests/skill-local.spec.ts

@@ -42,6 +42,14 @@ class TestFileSystem extends FileSystem {
     return { targetKey: path as never, displayPath: path }
   }
 
+  override processPath(target: FsTarget): string { return String(target.targetKey) }
+
+  override fileUrl(target: FsTarget): string { return `file://${target.targetKey}` }
+
+  override contains(parent: FsTarget, child: FsTarget): boolean {
+    return child.targetKey === parent.targetKey || String(child.targetKey).startsWith(`${parent.targetKey}/`)
+  }
+
   override async stat(target: FsTarget, signal?: AbortSignal): Promise<FsInfo | undefined> {
     this.statSignals.push(signal)
     if (this.failStatPaths.has(target.displayPath)) throw new FsError('stat failed', 'FS_NOT_FOUND')
@@ -84,6 +92,12 @@ class TestFileSystem extends FileSystem {
     return text
   }
 
+  override async readTextBounded(target: FsTarget, maxBytes: number, signal?: AbortSignal): Promise<string> {
+    const text = await this.readText(target, signal)
+    if (Buffer.byteLength(text) > maxBytes) throw new Error('too large')
+    return text
+  }
+
   override async streamText(_target: FsTarget): Promise<AsyncIterable<string>> {
     throw new Error('not needed in skill tests')
   }