feat: add schema helper aliases (latest)

- Add schemas/latest.ts and schemas_loose/latest.ts as aliases to current version
- Update constants.ts to use latest.ts instead of hardcoded version imports
- This makes version updates easier - only need to update latest.ts pointer

src/schemas/index.ts

@@ -1,6 +1,7 @@
 export * as v0_1 from "./0.1.js";
 export * as v0_2 from "./0.2.js";
+export * as latest from "./latest.js";
 export {
   MANIFEST_VERSION as CURRENT_MANIFEST_VERSION,
   McpbManifestSchema,
-} from "./0.2.js";
+} from "./latest.js";

src/schemas/latest.ts

@@ -0,0 +1 @@
+export * from "./0.2.js";