fix: remove unused @langchain/community peer dep, add langchain to langgraph-js agent, add postcss config to mcp-apps threejs-server

- Remove @langchain/community from sdk-js peerDependencies (unused,
  was blocking @langchain/core@1.x resolution)
- Add langchain@^1.0.0 to langgraph-js agent deps to prevent
  transitive resolution to 0.3.x
- Add postcss.config.mjs to mcp-apps threejs-server

Author: AlemTuzlak

examples/integrations/langgraph-js/agent/package.json

@@ -15,6 +15,7 @@
     "@langchain/langgraph": "1.0.2",
     "@langchain/langgraph-checkpoint": "1.0.0",
     "@langchain/openai": "^1.1.3",
+    "langchain": "^1.0.0",
     "zod": "^3.23.8"
   },
   "devDependencies": {

examples/integrations/mcp-apps/threejs-server/postcss.config.mjs

@@ -0,0 +1,5 @@
+const config = {
+  plugins: [],
+};
+
+export default config;

packages/sdk-js/package.json

@@ -79,7 +79,6 @@
     "vitest": "^3.2.4"
   },
   "peerDependencies": {
-    "@langchain/community": "^0.3.58",
     "@langchain/core": ">=0.4.0 <2.0.0",
     "@langchain/langgraph": ">=0.4.0 <2.0.0",
     "langchain": ">=1.0.0",