feat(debug): enable Python debug workflow and debug server integration

Adds an end-to-end Python debug workflow for the extension.
Includes a new prepare-debug.ps1 script and a VS Code task.
Extends the Python server and extension to coordinate a debug session and safe startup.

- Add prepare-debug.ps1 and a VS Code task to build the debug bundle
- Enable Python debug wiring in the server and tests
- Ensure a single stable Python debug session during startup

client/package.json

@@ -12,6 +12,7 @@
     "vscode-languageclient": "^9.0.1"
   },
   "devDependencies": {
+    "@types/fs-extra": "^11.0.4",
     "@types/node": "^22.10.5",
     "@types/vscode": "^1.96.0"
   }