Add /lsp-servers, /lsp-disable, /lsp-enable, and /lsp-destroy TUI commands.
Disabled servers are tracked in-memory per-extension-instance; the shared
daemon is never mutated by disable/enable. When all servers are disabled,
LSP tools are removed from the active tool set so the LLM won't attempt them.
Also adds a destroy_server daemon operation that kills running LspClient
entries by server ID or all entries.
