chore: officially migrate to submodule (#4502)

* remove apps/core and apps/fern

* fix precommit

* add submodule updates in workflows

* submodule

* remove core tests

* update core revision

* Add submodules: true to all GitHub workflows

- Ensure all workflows can access git submodules
- Add submodules support to deployment, test, and CI workflows
- Fix YAML syntax issues in workflow files

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

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

* remove core-lint

* upgrade core with latest main of oss

---------

Co-authored-by: Claude <noreply@anthropic.com>

examples/docs/node/tsconfig.json

@@ -1,18 +0,0 @@
-{
-  "compilerOptions": {
-    "target": "es2017",
-    "module": "esnext",
-    "lib": ["es2017", "dom"],
-    "declaration": true,
-    "strict": true,
-    "moduleResolution": "node",
-    "esModuleInterop": true,
-    "skipLibCheck": true,
-    "forceConsistentCasingInFileNames": true,
-    "outDir": "./dist",
-    "rootDir": ".",
-    "resolveJsonModule": true
-  },
-  "include": ["*.ts"],
-  "exclude": ["node_modules", "dist"]
-}