Fix/ripgrep fallback (#1273)

* fix: tmp 目录改用 os.tmpdir() + ripgrep 缺失时自动 fallback 系统 rg

1. Shell.ts / imagePaste.ts / filesystem.ts: Linux/macOS 默认 tmp 路径
   从硬编码 '/tmp' 改为 os.tmpdir()，自动适配 Termux/Android 等无 /tmp
   的环境；macOS 桌面零变化；CLAUDE_CODE_TMPDIR 仍优先级最高。

2. ripgrep.ts: builtin rg 二进制缺失时（Android/Termux、不完整安装）
   自动 fallback 到 PATH 上的系统 rg，通过 note 字段携带人读提示；
   /doctor 渲染 note；init 启动时写一行 stderr warning。

Co-Authored-By: glm-5.2 <zai-org@claude-code-best.win>

* fix: review fix — ripgrep note 文案修正 + init catch 加调试日志

- ripgrep "no ripgrep available" note 去掉无意义的 USE_BUILTIN_RIPGREP=0 建议
- init.ts ripgrep status check 的空 catch 加 logForDebugging

Co-Authored-By: glm-5.2 <zai-org@claude-code-best.win>

---------

Co-authored-by: glm-5.2 <zai-org@claude-code-best.win>

src/utils/__tests__/ripgrepConfig.test.ts

@@ -0,0 +1,75 @@
+import { afterAll, beforeAll, describe, expect, test } from 'bun:test'
+import { mkdirSync, rmSync, writeFileSync } from 'fs'
+import { join } from 'path'
+
+// Test the pure fallback function directly — no mock.module needed,
+// so this test cannot pollute other tests in the same Bun process.
+// See CLAUDE.md "Mock 使用规范" for why we avoid business-module mocking.
+const { resolveBuiltinWithFallback } = await import('../ripgrep.js')
+
+// Real temp dir with a real (or removed) fake rg binary to control existsSync.
+const tmpDir = join(
+  globalThis.process.env.TMPDIR || '/tmp',
+  'ripgrep-config-test',
+)
+const vendorDir = join(
+  tmpDir,
+  'vendor',
+  'ripgrep',
+  `${process.arch}-${process.platform}`,
+)
+const rgPath = join(vendorDir, process.platform === 'win32' ? 'rg.exe' : 'rg')
+
+describe('resolveBuiltinWithFallback', () => {
+  beforeAll(() => {
+    mkdirSync(vendorDir, { recursive: true })
+    writeFileSync(rgPath, '')
+  })
+
+  afterAll(() => {
+    rmSync(tmpDir, { recursive: true, force: true })
+  })
+
+  test('builtin exists -> mode=builtin, no note', () => {
+    const result = resolveBuiltinWithFallback(rgPath)
+    expect(result.mode).toBe('builtin')
+    expect(result.command).toBe(rgPath)
+    expect(result.note).toBeUndefined()
+  })
+
+  test('builtin missing + system rg available -> mode=system, note set', () => {
+    rmSync(rgPath)
+    const result = resolveBuiltinWithFallback(
+      rgPath,
+      '/usr/local/bin/rg', // explicit system rg path
+      'testplatform',
+    )
+    expect(result.mode).toBe('system')
+    expect(result.command).toBe('rg')
+    expect(result.note).toContain('fallback')
+    expect(result.note).toContain('testplatform')
+    // Restore for subsequent tests
+    writeFileSync(rgPath, '')
+  })
+
+  test('builtin missing + system rg missing -> mode=builtin, note set', () => {
+    rmSync(rgPath)
+    const result = resolveBuiltinWithFallback(
+      rgPath,
+      null, // no system rg
+      'testplatform',
+    )
+    expect(result.mode).toBe('builtin')
+    expect(result.command).toBe(rgPath)
+    expect(result.note).toContain('no ripgrep available')
+    expect(result.note).toContain('testplatform')
+    writeFileSync(rgPath, '')
+  })
+
+  test('uses process.platform when platform param omitted', () => {
+    rmSync(rgPath)
+    const result = resolveBuiltinWithFallback(rgPath, null)
+    expect(result.note).toContain(process.platform)
+    writeFileSync(rgPath, '')
+  })
+})