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>

package.json

@@ -26,14 +26,16 @@
       "types": "./dist/cli.d.ts",
       "import": "./dist/cli.js",
       "require": "./dist/cli.js"
-    }
+    },
+    "./mcpb-manifest.schema.json": "./dist/mcpb-manifest.schema.json"
   },
   "bin": "dist/cli/cli.js",
   "files": [
-    "dist"
+    "dist",
+    "schemas"
   ],
   "scripts": {
-    "build": "yarn run build:code",
+    "build": "yarn run build:code && yarn run build:schema",
     "build:code": "tsc",
     "build:schema": "node ./scripts/build-mcpb-schema.js",
     "dev": "tsc --watch",
@@ -71,7 +73,8 @@
     "ignore": "^7.0.5",
     "node-forge": "^1.3.1",
     "pretty-bytes": "^5.6.0",
-    "zod": "^3.25.67"
+    "zod": "^3.25.67",
+    "zod-to-json-schema": "^3.24.6"
   },
   "resolutions": {
     "@babel/helpers": "7.27.1",