Add Foundry Tauri v2 desktop app with UI polish

- Scaffold Tauri v2 desktop package (foundry/packages/desktop)
- Sidecar build script compiles backend into standalone Bun binary
- Frontend build script packages Vite output for Tauri webview
- macOS glass-effect app icon following Big Sur design standards
- Collapsible sidebars with smooth width transitions
- Inset content framing with borders and nested border-radius (Outer R = Inner R + Padding)
- iMessage-style chat bubble styling with proper corner radii
- Styled composer input with matching border-radius
- Vertical separator between chat and right sidebar
- Website download button component
- Cargo workspace exclude for standalone Tauri build

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

foundry/packages/desktop/src-tauri/src/lib.rs

@@ -0,0 +1,131 @@
+use std::sync::Mutex;
+use tauri::{AppHandle, Manager};
+use tauri_plugin_shell::process::CommandChild;
+use tauri_plugin_shell::ShellExt;
+
+struct BackendState {
+    child: Mutex<Option<CommandChild>>,
+}
+
+#[tauri::command]
+fn get_backend_url() -> String {
+    "http://127.0.0.1:7741".to_string()
+}
+
+#[tauri::command]
+async fn backend_health() -> Result<bool, String> {
+    match reqwest::get("http://127.0.0.1:7741/api/rivet/metadata").await {
+        Ok(resp) => Ok(resp.status().is_success()),
+        Err(_) => Ok(false),
+    }
+}
+
+async fn wait_for_backend(timeout_secs: u64) -> Result<(), String> {
+    let start = std::time::Instant::now();
+    let timeout = std::time::Duration::from_secs(timeout_secs);
+
+    loop {
+        if start.elapsed() > timeout {
+            return Err(format!(
+                "Backend failed to start within {} seconds",
+                timeout_secs
+            ));
+        }
+
+        match reqwest::get("http://127.0.0.1:7741/api/rivet/metadata").await {
+            Ok(resp) if resp.status().is_success() => return Ok(()),
+            _ => {}
+        }
+
+        tokio::time::sleep(std::time::Duration::from_millis(250)).await;
+    }
+}
+
+fn spawn_backend(app: &AppHandle) -> Result<(), String> {
+    let sidecar = app
+        .shell()
+        .sidecar("sidecars/foundry-backend")
+        .map_err(|e| format!("Failed to create sidecar command: {}", e))?
+        .args(["start", "--host", "127.0.0.1", "--port", "7741"]);
+
+    let (mut rx, child) = sidecar
+        .spawn()
+        .map_err(|e| format!("Failed to spawn backend sidecar: {}", e))?;
+
+    // Store the child process handle for cleanup
+    let state = app.state::<BackendState>();
+    *state.child.lock().unwrap() = Some(child);
+
+    // Log sidecar stdout/stderr in a background task
+    tauri::async_runtime::spawn(async move {
+        use tauri_plugin_shell::process::CommandEvent;
+        while let Some(event) = rx.recv().await {
+            match event {
+                CommandEvent::Stdout(line) => {
+                    eprintln!("[foundry-backend] {}", String::from_utf8_lossy(&line));
+                }
+                CommandEvent::Stderr(line) => {
+                    eprintln!("[foundry-backend] {}", String::from_utf8_lossy(&line));
+                }
+                CommandEvent::Terminated(payload) => {
+                    eprintln!(
+                        "[foundry-backend] process exited with code {:?}",
+                        payload.code
+                    );
+                    break;
+                }
+                CommandEvent::Error(err) => {
+                    eprintln!("[foundry-backend] error: {}", err);
+                    break;
+                }
+                _ => {}
+            }
+        }
+    });
+
+    Ok(())
+}
+
+#[cfg_attr(mobile, tauri::mobile_entry_point)]
+pub fn run() {
+    tauri::Builder::default()
+        .plugin(tauri_plugin_shell::init())
+        .manage(BackendState {
+            child: Mutex::new(None),
+        })
+        .invoke_handler(tauri::generate_handler![get_backend_url, backend_health])
+        .setup(|app| {
+            // In debug mode, assume the developer is running the backend externally
+            if cfg!(debug_assertions) {
+                eprintln!("[foundry-desktop] Dev mode: skipping sidecar spawn. Run the backend separately.");
+                return Ok(());
+            }
+
+            let handle = app.handle().clone();
+            tauri::async_runtime::spawn(async move {
+                if let Err(e) = spawn_backend(&handle) {
+                    eprintln!("[foundry-desktop] Failed to start backend: {}", e);
+                    return;
+                }
+
+                match wait_for_backend(30).await {
+                    Ok(()) => eprintln!("[foundry-desktop] Backend is ready."),
+                    Err(e) => eprintln!("[foundry-desktop] {}", e),
+                }
+            });
+
+            Ok(())
+        })
+        .on_window_event(|window, event| {
+            if let tauri::WindowEvent::Destroyed = event {
+                let state = window.state::<BackendState>();
+                let child = state.child.lock().unwrap().take();
+                if let Some(child) = child {
+                    let _ = child.kill();
+                    eprintln!("[foundry-desktop] Backend sidecar killed.");
+                }
+            }
+        })
+        .run(tauri::generate_context!())
+        .expect("error while running Foundry");
+}