feat: file-based logging to wraith.log for MCP startup diagnostics

env_logger was never initialized so log::info/error went nowhere.
Added write_log() that appends to data_dir/wraith.log with timestamps.
Logs MCP server startup success/failure and any panics.

Check: %APPDATA%\Wraith\wraith.log (Windows)
       ~/Library/Application Support/Wraith/wraith.log (macOS)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/src/lib.rs

@@ -91,9 +91,29 @@ pub fn data_directory() -> PathBuf {
     PathBuf::from(".")
 }
 
+fn write_log(path: &std::path::Path, msg: &str) -> std::io::Result<()> {
+    use std::io::Write;
+    let mut f = std::fs::OpenOptions::new().create(true).append(true).open(path)?;
+    let elapsed = std::time::SystemTime::now()
+        .duration_since(std::time::UNIX_EPOCH)
+        .unwrap_or_default()
+        .as_secs();
+    writeln!(f, "[{}] {}", elapsed, msg)
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
-    let app_state = AppState::new(data_directory()).expect("Failed to init AppState");
+    // Initialize file-based logging to data_dir/wraith.log
+    let log_path = data_directory().join("wraith.log");
+    let _ = write_log(&log_path, "=== Wraith starting ===");
+
+    let app_state = match AppState::new(data_directory()) {
+        Ok(s) => s,
+        Err(e) => {
+            let _ = write_log(&log_path, &format!("FATAL: AppState init failed: {}", e));
+            panic!("Failed to init AppState: {}", e);
+        }
+    };
     app_state.theme.seed_builtins();
 
     tauri::Builder::default()
@@ -109,25 +129,30 @@ pub fn run() {
             }
 
             // Start MCP and error watcher — completely non-fatal.
-            // These are nice-to-have services that must never crash the app.
             {
                 use tauri::Manager;
+                let log_file = data_directory().join("wraith.log");
+                let _ = write_log(&log_file, "Setup: starting MCP and error watcher");
+
                 if let Ok(state) = std::panic::catch_unwind(std::panic::AssertUnwindSafe(|| {
                     app.state::<AppState>().inner().clone_services()
                 })) {
                     let (ssh, rdp, sftp, scrollback, watcher) = state;
+                    let _ = write_log(&log_file, "Setup: cloned services OK");
 
                     let app_handle = app.handle().clone();
                     mcp::error_watcher::start_error_watcher(watcher, scrollback.clone(), app_handle);
+                    let _ = write_log(&log_file, "Setup: error watcher started");
 
+                    let log_file2 = log_file.clone();
                     tauri::async_runtime::spawn(async move {
                         match mcp::server::start_mcp_server(ssh, rdp, sftp, scrollback).await {
-                            Ok(port) => log::info!("MCP server started on localhost:{}", port),
-                            Err(e) => log::error!("Failed to start MCP server: {}", e),
+                            Ok(port) => { let _ = write_log(&log_file2, &format!("MCP server started on localhost:{}", port)); }
+                            Err(e) => { let _ = write_log(&log_file2, &format!("MCP server FAILED: {}", e)); }
                         }
                     });
                 } else {
-                    log::error!("MCP/error watcher startup failed — continuing without MCP");
+                    let _ = write_log(&log_file, "MCP startup panicked — continuing without MCP");
                 }
             }