feat: add DSH plugin marketplace and shared MCP

GoodBuddy could share Skills across runtimes, but custom MCP remained limited and DeepSeek Harness could not manage third-party extensions. The app now provides a default-off DSH npm marketplace with managed installation, configuration, failure isolation, and packaged npm support, while assigned custom MCP is available to managed OpenCode, Continue Agent, and DeepSeek Harness in Execute.

Third-party DSH install scripts, initialization, and tools run with the current user's permissions. Ask remains read-only at dispatch, and turning off the marketplace hides management without disabling installed plugins.

Release note: 新增默认关闭的 DSH 插件市场，并让自定义 MCP 可分配给 OpenCode、Continue 和 DeepSeek Harness；安装第三方插件前会明确提示当前用户权限边界。

src/main/agent/deepseek-harness-utility-launcher.test.ts

@@ -44,6 +44,7 @@ async function fixture() {
     writeFile(hostPath, '', 'utf8')
   ])
   return {
+    root,
     dshHome,
     hostPath,
     launchOptions: {
@@ -52,7 +53,8 @@ async function fixture() {
       baseUrl: 'https://gateway.example/openai/v1',
       model: 'qwen-plus',
       credentialRefs: [DEEPSEEK_HARNESS_CREDENTIAL_REF],
-      skillPackages: []
+      skillPackages: [],
+      extensionPackages: []
     }
   }
 }
@@ -63,7 +65,8 @@ describe('DeepSeek Harness utility launcher', () => {
       parseHarnessControlMessage({
         protocol: DEEPSEEK_HARNESS_CONTROL_PROTOCOL,
         version: DEEPSEEK_HARNESS_CONTROL_VERSION,
-        type: 'ready'
+        type: 'ready',
+        failedExtensionIds: []
       })
     ).toMatchObject({ type: 'ready' })
     expect(
@@ -71,6 +74,7 @@ describe('DeepSeek Harness utility launcher', () => {
         protocol: DEEPSEEK_HARNESS_CONTROL_PROTOCOL,
         version: DEEPSEEK_HARNESS_CONTROL_VERSION,
         type: 'ready',
+        failedExtensionIds: [],
         apiKey: 'must-not-pass'
       })
     ).toBeUndefined()
@@ -105,7 +109,8 @@ describe('DeepSeek Harness utility launcher', () => {
     utility.emit('message', {
       protocol: DEEPSEEK_HARNESS_CONTROL_PROTOCOL,
       version: DEEPSEEK_HARNESS_CONTROL_VERSION,
-      type: 'ready'
+      type: 'ready',
+      failedExtensionIds: []
     })
 
     await expect(launching).resolves.toMatchObject({
@@ -122,6 +127,87 @@ describe('DeepSeek Harness utility launcher', () => {
     )
   })
 
+  it('persists extension startup failures before exposing the child', async () => {
+    const { root, dshHome, hostPath, launchOptions } =
+      await fixture()
+    const entrypoint = join(root, 'greet.mjs')
+    await writeFile(entrypoint, 'export function apply() {}\n', 'utf8')
+    const utility = new FakeUtility()
+    const onExtensionStartupFailures = vi.fn(async () => undefined)
+    const launcher = createDeepSeekHarnessUtilityLauncher({
+      bundledHostPath: hostPath,
+      dshHome,
+      environment: {},
+      fork: () => utility as never,
+      onExtensionStartupFailures
+    })
+
+    const launching = launcher({
+      ...launchOptions,
+      extensionPackages: [
+        {
+          id: 'greet',
+          entrypoint,
+          configuration: {}
+        }
+      ]
+    })
+    await vi.waitFor(() =>
+      expect(utility.messages).toHaveLength(1)
+    )
+    utility.emit('message', {
+      protocol: DEEPSEEK_HARNESS_CONTROL_PROTOCOL,
+      version: DEEPSEEK_HARNESS_CONTROL_VERSION,
+      type: 'ready',
+      failedExtensionIds: ['greet']
+    })
+
+    await expect(launching).resolves.toBeDefined()
+    expect(onExtensionStartupFailures).toHaveBeenCalledWith([
+      'greet'
+    ])
+  })
+
+  it('fails when the Host exits while startup failures are being persisted', async () => {
+    const { dshHome, hostPath, launchOptions } = await fixture()
+    const utility = new FakeUtility()
+    let finishPersistence!: () => void
+    const persistence = new Promise<void>((resolve) => {
+      finishPersistence = resolve
+    })
+    const onExtensionStartupFailures = vi.fn(() => persistence)
+    const terminateProcess = vi.fn()
+    const launcher = createDeepSeekHarnessUtilityLauncher({
+      bundledHostPath: hostPath,
+      dshHome,
+      environment: {},
+      fork: () => utility as never,
+      terminateProcess,
+      onExtensionStartupFailures
+    })
+
+    const launching = launcher(launchOptions)
+    await vi.waitFor(() =>
+      expect(utility.messages).toHaveLength(1)
+    )
+    utility.emit('message', {
+      protocol: DEEPSEEK_HARNESS_CONTROL_PROTOCOL,
+      version: DEEPSEEK_HARNESS_CONTROL_VERSION,
+      type: 'ready',
+      failedExtensionIds: ['greet']
+    })
+    await vi.waitFor(() =>
+      expect(onExtensionStartupFailures).toHaveBeenCalledOnce()
+    )
+    utility.emit('exit', 9)
+
+    await expect(launching).rejects.toThrow(
+      'Host 启动前退出（code 9）'
+    )
+    expect(terminateProcess).toHaveBeenCalledOnce()
+    finishPersistence()
+  })
+
   it('fails closed on an invalid Host startup message', async () => {
     const { dshHome, hostPath, launchOptions } = await fixture()
     const utility = new FakeUtility()