fix(mcp): use zod/v3 for compatibility with mcp-handler

The mcp-handler package internally depends on @modelcontextprotocol/[email protected],
which uses zod-to-json-schema that is incompatible with Zod 4. This caused
the `component` parameter in `get_ai_elements_component` tool to not be
exposed in the inputSchema (empty properties object).

Changes:
- Import zod from "zod/v3" instead of "zod" for backward compatibility
- Replace z.enum() with z.string().describe() for better schema generation
- Improve error message to list available components when not found

Author: liuhaitian

apps/registry/app/api/[transport]/route.ts

@@ -3,7 +3,7 @@ import { join } from "node:path";
 import { track } from "@vercel/analytics/server";
 import { createMcpHandler } from "mcp-handler";
 import type { RegistryItem } from "shadcn/schema";
-import { z } from "zod";
+import { z } from "zod/v3";
 
 const packageDir = join(process.cwd(), "..", "..", "packages", "elements");
 const srcDir = join(packageDir, "src");
@@ -38,7 +38,13 @@ const handler = createMcpHandler(
     server.tool(
       "get_ai_elements_component",
       "Provides information about an AI Elements component.",
-      { component: z.enum(componentNames as [string, ...string[]]) },
+      {
+        component: z
+          .string()
+          .describe(
+            `Component name. Available: ${componentNames.join(", ")}`
+          ),
+      },
       async ({ component }) => {
         const tsxFile = tsxFiles.find(
           (file) => file.name === `${component}.tsx`
@@ -47,7 +53,10 @@ const handler = createMcpHandler(
         if (!tsxFile) {
           return {
             content: [
-              { type: "text", text: `Component ${component} not found` },
+              {
+                type: "text",
+                text: `Component "${component}" not found. Available components: ${componentNames.join(", ")}`,
+              },
             ],
           };
         }