feat(lsp): implement LSP client and server management

- Added LspClient for handling communication with LSP servers, including methods for initialization, notifications, and requests.
- Introduced LspManager to manage multiple LSP server connections, allowing for connection, disconnection, and retrieval of server capabilities.
- Created tools for connecting to LSP servers, retrieving diagnostics, hover information, code completion, definitions, and references.
- Enhanced UI rendering to display token usage and settings in the overlay.
- Updated status bar to show current token usage and selected provider/model.

src-misc/system-tools.txt

@@ -39,5 +39,20 @@ Workflow:
   multi-step tasks needing parallel analysis or verification. Pass inline
   scripts with agent(), parallel(), and pipeline() primitives.
 
+Language Server Protocol (LSP) tools:
+- lsp_connect(name, command, args?, language_id) — Start an LSP server for a
+  programming language (e.g. 'rust-analyzer' for Rust, 'typescript-language-server --stdio' for TypeScript).
+- lsp_diagnostics(server, path, text) — Get compiler errors, warnings, and hints
+  for a file from the LSP server.
+- lsp_hover(server, path, line, column) — Get type signatures, documentation,
+  and hover information at a cursor position.
+- lsp_completion(server, path, line, column) — Get code completion suggestions
+  at a cursor position.
+- lsp_definition(server, path, line, column) — Find the definition location of
+  a symbol at the cursor.
+- lsp_references(server, path, line, column) — Find all references to a symbol
+  across the project.
+- lsp_disconnect(name) — Disconnect from a running LSP server.
+
 Each write/edit call MUST include a non-empty reason argument explaining
 why the change is being made. This is enforced deterministically.