feat(Handler/ui): Add native dialog handler for extension messages

- Introduce `ui` handler module in Mountain backend to process UI commands from Cocoon shim
- Implement `handle_show_message` using Tauri's native dialog API instead of web-based alerts
- Map VS Code extension message severity levels (Error/Warn/Info) to native dialog titles
- Add structured logging for extension message events through stdio
- Improve code formatting with rustfmt for better maintainability

This change replaces Electron's web-based dialogs with Tauri's native implementations, aligning with Land's performance goals by reducing webview interaction overhead. The handler enables VS Code extensions using `window.showErrorMessage`/`showWarningMessage` APIs to function through Cocoon shim layer while maintaining native UI consistency.

Author: NikolaRHristov

Source/Library.rs

@@ -40,4 +40,6 @@ pub mod handlers {
 	pub mod storage;
 
 	pub mod terminal;
+
+	pub mod ui;
 }

Source/handlers/ui.rs

@@ -25,15 +25,21 @@ use tauri::{Runtime, Window};
 
 // Handler for ui_showMessage proxied from Cocoon shim
 pub async fn handle_show_message<R:Runtime>(window:Window<R>, params:Value) -> Result<Value, String> {
-	let severity = params.get("severity").and_then(|v| v.as_u64()).unwrap_or(2); // Default Info
+	// Default Info
+	let severity = params.get("severity").and_then(|v| v.as_u64()).unwrap_or(2);
+
 	let message = params.get("message").and_then(|v| v.as_str()).unwrap_or("");
+
 	println!("[UI Handler] ShowMessage severity={}, message={}", severity, message);
 
 	// Map severity if needed
 	let title = match severity {
-		1 => "Extension Warning", // Warn
-		0 => "Extension Error",   // Error
-		_ => "Extension Info",    // Info/default
+		// Warn
+		1 => "Extension Warning",
+		// Error
+		0 => "Extension Error",
+		// Info/default
+		_ => "Extension Info",
 	};
 
 	// Use Tauri's dialog API