fix: improve JSON schema generation and publishing

- Refactor JSON schema generation to use zod-to-json-schema
- Publish manifest schema to schemas/ directory
- Update package.json exports for schema files
- Add WIP version 0.3 support
- Clean up schema generation scripts

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/build-mcpb-schema.js

@@ -1,8 +1,8 @@
 import {
   McpbManifestSchema,
   McpbSignatureInfoSchema,
-} from "../dist/schemas.js";
-import * as z from "zod/v4";
+} from "../dist/schemas/latest.js";
+import { zodToJsonSchema } from "zod-to-json-schema";
 import fs from "node:fs/promises";
 import path from "node:path";
 
@@ -11,15 +11,23 @@ const schemasToWrite = {
   "mcpb-signature-info": McpbSignatureInfoSchema,
 };
 
-await fs.mkdir(path.join(import.meta.dirname, "../dist"), { recursive: true });
+const distDir = path.join(import.meta.dirname, "../dist");
+const schemasDir = path.join(import.meta.dirname, "../schemas");
 
+// Generate all schemas to dist/
+await fs.mkdir(distDir, { recursive: true });
 for (const key in schemasToWrite) {
-  const schema = z.toJSONSchema(schemasToWrite[key]);
-  await fs.writeFile(
-    path.join(import.meta.dirname, "../dist", `${key}.schema.json`),
-    JSON.stringify(schema, null, 2),
-    {
-      encoding: "utf8",
-    },
-  );
+  const schema = zodToJsonSchema(schemasToWrite[key]);
+  const filePath = path.join(distDir, `${key}.schema.json`);
+  await fs.writeFile(filePath, JSON.stringify(schema, null, 2), {
+    encoding: "utf8",
+  });
 }
+
+// Generate only manifest schema to schemas/
+await fs.mkdir(schemasDir, { recursive: true });
+const manifestSchema = zodToJsonSchema(McpbManifestSchema);
+const manifestPath = path.join(schemasDir, "mcpb-manifest.schema.json");
+await fs.writeFile(manifestPath, JSON.stringify(manifestSchema, null, 2), {
+  encoding: "utf8",
+});