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

server/src/lsp_server.py

@@ -704,7 +704,13 @@ def initialized(_params: lsp.InitializedParams):
 
     def index_workspace():
         try:
-            root = LSP_SERVER.workspace.root_path
+            try:
+                root = LSP_SERVER.workspace.root_path
+            except RuntimeError:
+                root = None
+            if not root:
+                log_to_output("Background indexing skipped: no workspace folder is open.")
+                return
             log_to_output("Background indexing started...")
             root_path = pathlib.Path(root)
             skipped_directories = {