- 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
