refactor(lsp): replace LSPManager with controller-based architecture

- Remove legacy LSPManager dialog implementation
- Introduce LSPController as the central LSP entry point
- Route UI interactions through lsp_controller.lsp_manager_ui
- Move client lifecycle handling out of ProviderResponseCache
- Simplify completion cache and matcher filtering
- Improve LSP completion item parsing with safer fallbacks
- Modernize typing (Python 3.10 union syntax)
- Remove unused imports and dead code
- Use GLib.idle_add for safe UI scrolling operations
- Minor comment and spelling fixes

plugins/code/ui/lsp_manager/handlers/python.py

@@ -0,0 +1,12 @@
+# Python imports
+
+# Lib imports
+
+# Application imports
+from .default import DefaultHandler
+
+
+
+class PythonHandler(DefaultHandler):
+    """Uses default handling, can override if Python needs special logic."""
+    ...