chore: add .gitignore entry for generated json-schema files

Author: hotlong

.changeset/gitignore-json-schema.md

@@ -0,0 +1,10 @@
+---
+"@objectstack/spec": patch
+"@objectstack/cli": patch
+---
+
+chore: exclude generated json-schema from git tracking
+
+- Add `packages/spec/json-schema/` to `.gitignore` (1277 generated files, 5MB)
+- JSON schema files are still generated during `pnpm build` and included in npm publish via `files` field
+- Fix studio module resolution logic for better compatibility