refactor(evals): migrate skill extraction to componentEvalTest

Replaces the evalTest approach (full CLI subprocess + loadCliConfig) with
componentEvalTest (in-process makeFakeConfig + direct startMemoryService).

Key changes:
- ComponentRig now creates an isolated homeDir and stubs GEMINI_CLI_HOME
  after auth to isolate storage paths (sessions, skills, extraction state).
- ComponentRig.cleanup() calls config.dispose() and vi.unstubAllEnvs().
- Skill extraction evals pass approvalMode: YOLO to auto-approve tool
  calls (write_file/read_file) in non-interactive mode.
- Removes ~100 lines of boilerplate (withRigStorage, waitForExtractionState,
  loadCliConfig, loadSettings, process.chdir).

Author: SandyTao520

evals/component-test-helper.ts

@@ -16,6 +16,7 @@ import fs from 'node:fs';
 import path from 'node:path';
 import os from 'node:os';
 import { randomUUID } from 'node:crypto';
+import { vi } from 'vitest';
 import {
   Config,
   type ConfigParameters,
@@ -52,6 +53,7 @@ export interface ComponentEvalCase extends BaseEvalCase {
 export class ComponentRig {
   public config: Config | undefined;
   public testDir: string;
+  public homeDir: string;
   public sessionId: string;
 
   constructor(
@@ -61,6 +63,9 @@ export class ComponentRig {
     this.testDir = fs.mkdtempSync(
       path.join(os.tmpdir(), `gemini-component-rig-${uniqueId.slice(0, 8)}-`),
     );
+    this.homeDir = fs.mkdtempSync(
+      path.join(os.tmpdir(), `gemini-component-home-${uniqueId.slice(0, 8)}-`),
+    );
     this.sessionId = `test-session-${uniqueId}`;
   }
 
@@ -89,12 +94,23 @@ export class ComponentRig {
     this.config = makeFakeConfig(configParams);
     await this.config.initialize();
 
-    // Refresh auth using USE_GEMINI to initialize the real BaseLlmClient
+    // Refresh auth using USE_GEMINI to initialize the real BaseLlmClient.
+    // This must happen BEFORE stubbing GEMINI_CLI_HOME because OAuth credential
+    // lookup resolves through homedir() → GEMINI_CLI_HOME.
     await this.config.refreshAuth(AuthType.USE_GEMINI);
+
+    // Isolate storage paths (session files, skills, extraction state) by
+    // pointing GEMINI_CLI_HOME at a per-test temp directory.  Storage resolves
+    // global paths through `homedir()` which reads this env var.  This is set
+    // after auth so credential lookup uses the real home directory.
+    vi.stubEnv('GEMINI_CLI_HOME', this.homeDir);
   }
 
   async cleanup() {
+    await this.config?.dispose();
+    vi.unstubAllEnvs();
     fs.rmSync(this.testDir, { recursive: true, force: true });
+    fs.rmSync(this.homeDir, { recursive: true, force: true });
   }
 }