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/deepseek-harness-host.ts

@@ -25,6 +25,10 @@ import {
   createBoundedAcpStream,
   type GoodBuddyHarnessControlConfig
 } from './agent/goodbuddy-harness-control-plane'
+import {
+  loadControlledHarnessExtensions,
+  type ControlledHarnessExtensionPackage
+} from './agent/deepseek-harness-extension-loader'
 import type { Stream } from '@agentclientprotocol/sdk'
 import { isDeepSeekHarnessCompatibleBaseUrl } from '../shared/deepseek-harness-compatibility'
 
@@ -45,11 +49,17 @@ export type ControlledHarnessHostConfig = Omit<
     id: string
     directory: string
   }[]
+  extensionPackages?: readonly ControlledHarnessExtensionPackage[]
 }
 
 export type ControlledHarnessHost = {
   readonly context: Context
   readonly controlPlane: GoodBuddyHarnessControlPlane
+  readonly failedExtensionIds: readonly string[]
+  readonly extensionFailures: readonly {
+    id: string
+    message: string
+  }[]
   dispose(): Promise<void>
 }
 
@@ -123,7 +133,25 @@ async function canonicalizeHostConfig(
       return { ...skill, directory }
     })
   )
-  return { ...config, workspace, dshHome, skillPackages }
+  const extensionPackages = await Promise.all(
+    (config.extensionPackages ?? []).map(async (extension) => {
+      const entrypoint = await realpath(extension.entrypoint)
+      const metadata = await stat(entrypoint)
+      if (!metadata.isFile()) {
+        throw new Error(
+          'Controlled Harness extension entrypoint must be a file'
+        )
+      }
+      return { ...extension, entrypoint }
+    })
+  )
+  return {
+    ...config,
+    workspace,
+    dshHome,
+    skillPackages,
+    extensionPackages
+  }
 }
 
 async function loadControlledSkills(
@@ -175,9 +203,10 @@ async function loadControlledSkills(
 /**
  * Boots a fixed, programmatic Cordis graph. It never imports app-boot, a
  * profile loader, settings-file, local credentials, persistence, telemetry,
- * web, HMR, marketplace/plugin discovery, direct MCP clients, jobs,
- * subagents, hooks, or workflow packages. The control plane registers only
- * Main-selected Skill snapshots and Main-mediated MCP tool proxies.
+ * web, HMR, marketplace discovery, direct MCP clients, jobs, subagents,
+ * hooks, or workflow packages. The control plane registers Main-selected
+ * Skill snapshots, Main-mediated MCP tool proxies, and explicitly enabled
+ * extension entrypoints.
  */
 export async function startControlledDeepSeekHarnessHost(
   input: ControlledHarnessHostConfig
@@ -256,6 +285,10 @@ export async function startControlledDeepSeekHarnessHost(
       )
     }
     await Promise.all(fibers)
+    const extensions = await loadControlledHarnessExtensions(
+      ctx,
+      config.extensionPackages ?? []
+    )
     const credentialProvider = ctx.credentials
     if (!(credentialProvider instanceof GoodBuddyCredentialProvider)) {
       throw new Error(
@@ -284,6 +317,8 @@ export async function startControlledDeepSeekHarnessHost(
     return {
       context: ctx,
       controlPlane,
+      failedExtensionIds: extensions.failedIds,
+      extensionFailures: extensions.failures,
       async dispose() {
         await controlPlane.dispose()
         await ctx.fiber.dispose()