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/app/lsp/mod.rs

@@ -0,0 +1,80 @@
+use std::sync::{Arc, Mutex};
+
+mod client;
+pub use client::{path_to_lsp_uri, LspClient};
+
+#[derive(Clone)]
+pub struct LspServer {
+    #[allow(dead_code)]
+    pub name: String,
+    #[allow(dead_code)]
+    pub command: String,
+    #[allow(dead_code)]
+    pub args: Vec<String>,
+    pub language_id: String,
+    pub client: Arc<Mutex<LspClient>>,
+}
+
+#[derive(Clone)]
+pub struct LspManager {
+    pub servers: Vec<LspServer>,
+}
+
+impl LspManager {
+    pub fn new() -> Self {
+        LspManager {
+            servers: Vec::new(),
+        }
+    }
+
+    pub fn connect(
+        &mut self,
+        name: &str,
+        command: &str,
+        args: &[String],
+        language_id: &str,
+    ) -> anyhow::Result<()> {
+        if self.servers.iter().any(|s| s.name == name) {
+            anyhow::bail!("LSP server '{}' is already connected", name);
+        }
+        let client = LspClient::spawn(command, args)?;
+        self.servers.push(LspServer {
+            name: name.to_string(),
+            command: command.to_string(),
+            args: args.to_vec(),
+            language_id: language_id.to_string(),
+            client: Arc::new(Mutex::new(client)),
+        });
+        Ok(())
+    }
+
+    #[allow(dead_code)]
+    pub fn find_server(&self, name: &str) -> Option<&LspServer> {
+        self.servers.iter().find(|s| s.name == name)
+    }
+
+    pub fn get_client(&self, name: &str) -> Option<Arc<Mutex<LspClient>>> {
+        self.servers.iter().find(|s| s.name == name).map(|s| s.client.clone())
+    }
+
+    pub fn disconnect(&mut self, name: &str) -> bool {
+        if let Some(server) = self.servers.iter().find(|s| s.name == name) {
+            if let Ok(mut client) = server.client.lock() {
+                let _ = client.shutdown();
+            }
+        }
+        let len = self.servers.len();
+        self.servers.retain(|s| s.name != name);
+        self.servers.len() < len
+    }
+
+    pub fn get_language_id(&self, name: &str) -> Option<String> {
+        self.servers.iter().find(|s| s.name == name).map(|s| s.language_id.clone())
+    }
+}
+
+impl Default for LspManager {
+    fn default() -> Self {
+        Self::new()
+    }
+}