Fix Desktop search-mcp takeover so web_search uses Bailian.

Drop nested Config.volatile that left the fiber inactive, unwrap the cordis
web proxy to pin/wrap search at runtime, and restore deepseek on disable.

Co-authored-by: Cursor <cursoragent@cursor.com>

scripts/_validate-config.mjs

@@ -0,0 +1,73 @@
+/**
+ * Reproduce Desktop Config validation for search-mcp.
+ * Usage: node scripts/_validate-config.mjs
+ */
+import { createRequire } from 'node:module'
+import { pathToFileURL } from 'node:url'
+import { join, dirname } from 'node:path'
+import { fileURLToPath } from 'node:url'
+
+const pkgRoot = join(dirname(fileURLToPath(import.meta.url)), '..')
+const nm = join(process.env.USERPROFILE || '', '.dsh', 'profiles', 'node_modules')
+const req = createRequire(join(nm, 'package.json'))
+const cordisUrl = pathToFileURL(req.resolve('@deepseek-ai/cordis')).href
+const { Context, Service } = await import(cordisUrl)
+const mod = await import(pathToFileURL(join(pkgRoot, 'lib', 'index.js')).href)
+
+class WebRuntime extends Service {
+  searchProviders = new Map()
+  searchProviderId = 'deepseek-official'
+  constructor(ctx) {
+    super(ctx, 'web')
+  }
+  registerSearchProvider(p) {
+    this.searchProviders.set(p.id, p)
+    return () => this.searchProviders.delete(p.id)
+  }
+  async search() {
+    return { used: this.searchProviderId }
+  }
+}
+
+function plugin(ctx, config) {
+  mod.apply(ctx, config)
+}
+plugin.inject = ['web']
+plugin.Config = mod.Config
+
+const root = new Context()
+try {
+  await root.plugin(WebRuntime)
+  await root.plugin(plugin, {
+    defaultServer: 'bailian',
+    maxResults: 8,
+    searchTimeoutMs: 30000,
+    servers: [{ id: 'bailian', kind: 'bailian', apiKeyEnv: 'DASHSCOPE_API_KEY' }],
+  })
+  const raw = root.web[Symbol.for('cordis.original')]
+  console.log(
+    JSON.stringify(
+      {
+        ok: true,
+        faceId: root.web.searchProviderId,
+        rawId: raw?.searchProviderId,
+        wrapped: !!raw?.search?.__searchMcpWrapped,
+      },
+      null,
+      2,
+    ),
+  )
+} catch (e) {
+  console.log(
+    JSON.stringify(
+      {
+        ok: false,
+        message: String(e?.message || e),
+        stack: String(e?.stack || '').slice(0, 1200),
+      },
+      null,
+      2,
+    ),
+  )
+  process.exit(1)
+}