chore: configure devcontainer Python venv persistence and normalize package-lock peer dependencies

- Added bind mount for .venv directory in devcontainer to persist Python virtual environment across container rebuilds
- Enabled updateRemoteUserUID for proper file permissions in devcontainer
- Normalized peer dependency flags in package-lock.json (removed inconsistent "peer": true from core dependencies, added to test-only dependencies)
- Added empty codex file placeholder
- Created comprehensive

.devcontainer/devcontainer.json

@@ -20,6 +20,10 @@
     "DISPLAY": ":1",
     "XDG_RUNTIME_DIR": "/tmp/runtime-vscode"
   },
+  "mounts": [
+    "source=${localWorkspaceFolder}/.venv,target=${containerWorkspaceFolder}/.venv,type=bind,consistency=cached"
+  ],
+  "updateRemoteUserUID": true,
   "postCreateCommand": ".devcontainer/postCreate.sh",
   "remoteUser": "vscode",
   "customizations": {