Add single-instance support and clean up scaffolding files

Ensure only one Vesper instance runs at a time. When a second
instance is launched with a file argument, the file is forwarded
to the existing window. Remove unused template SVGs and test file.

src-tauri/Cargo.lock

@@ -3703,6 +3703,21 @@ dependencies = [
  "zbus",
 ]
 
+[[package]]
+name = "tauri-plugin-single-instance"
+version = "2.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "dc61e4822b8f74d68278e09161d3e3fdd1b14b9eb781e24edccaabf10c420e8c"
+dependencies = [
+ "serde",
+ "serde_json",
+ "tauri",
+ "thiserror 2.0.18",
+ "tracing",
+ "windows-sys 0.60.2",
+ "zbus",
+]
+
 [[package]]
 name = "tauri-runtime"
 version = "2.10.0"
@@ -4281,7 +4296,7 @@ checksum = "0b928f33d975fc6ad9f86c8f283853ad26bdd5b10b7f1542aa2fa15e2289105a"
 
 [[package]]
 name = "vesper"
-version = "0.1.0"
+version = "1.0.1"
 dependencies = [
  "serde",
  "serde_json",
@@ -4290,6 +4305,7 @@ dependencies = [
  "tauri-plugin-dialog",
  "tauri-plugin-fs",
  "tauri-plugin-opener",
+ "tauri-plugin-single-instance",
 ]
 
 [[package]]

src-tauri/Cargo.toml

@@ -22,3 +22,6 @@ tauri-plugin-fs = "2"
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
 
+[target.'cfg(not(any(target_os = "android", target_os = "ios")))'.dependencies]
+tauri-plugin-single-instance = "2"
+

src-tauri/src/lib.rs

@@ -39,6 +39,31 @@ fn save_window_state(state: &WindowState) {
     }
 }
 
+#[derive(Serialize, Clone)]
+struct CliFile {
+    path: String,
+    content: String,
+}
+
+/// Try to read a markdown file from the given path string.
+fn read_md_file(file_arg: &str) -> Option<CliFile> {
+    let path = PathBuf::from(file_arg);
+    if !path.is_file() { return None; }
+    let ext = path.extension()?.to_str()?.to_lowercase();
+    if ext != "md" && ext != "markdown" && ext != "txt" { return None; }
+    let content = fs::read_to_string(&path).ok()?;
+    Some(CliFile {
+        path: path.to_string_lossy().to_string(),
+        content,
+    })
+}
+
+/// Returns the file path + content if the app was launched with a .md/.markdown/.txt argument.
+#[tauri::command]
+fn get_cli_file() -> Option<CliFile> {
+    env::args().nth(1).and_then(|a| read_md_file(&a))
+}
+
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
 pub fn run() {
     let data_dir = get_data_dir();
@@ -51,9 +76,23 @@ pub fn run() {
     );
 
     tauri::Builder::default()
+        .plugin(tauri_plugin_single_instance::init(|app, args, _cwd| {
+            // Second instance launched with a file — send it to the existing window
+            if let Some(file_arg) = args.get(1) {
+                if let Some(cli_file) = read_md_file(file_arg) {
+                    let _ = app.emit("open-file", cli_file);
+                }
+            }
+            // Focus the existing window
+            if let Some(window) = app.get_webview_window("main") {
+                let _ = window.unminimize();
+                let _ = window.set_focus();
+            }
+        }))
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_fs::init())
+        .invoke_handler(tauri::generate_handler![get_cli_file])
         .setup(|app| {
             let state = load_window_state();
             let window = app.get_webview_window("main").unwrap();
@@ -64,35 +103,12 @@ pub fn run() {
                 ));
             }
             if let (Some(w), Some(h)) = (state.width, state.height) {
-                let _ = window.set_size(tauri::Size::Physical(
-                    tauri::PhysicalSize::new(w, h),
-                ));
+                let _ = window.set_size(tauri::Size::Physical(tauri::PhysicalSize::new(w, h)));
             }
             if let Some(true) = state.maximized {
                 let _ = window.maximize();
             }
 
-            // If launched with a file argument (e.g. double-clicking a .md file),
-            // emit the path to the frontend so it can open it as a tab.
-            let args: Vec<String> = env::args().collect();
-            if let Some(file_arg) = args.get(1) {
-                let path = PathBuf::from(file_arg);
-                if path.is_file() {
-                    if let Some(ext) = path.extension().and_then(|e| e.to_str()) {
-                        let ext_lower = ext.to_lowercase();
-                        if ext_lower == "md" || ext_lower == "markdown" || ext_lower == "txt" {
-                            let path_str = path.to_string_lossy().to_string();
-                            let win = window.clone();
-                            // Emit after a short delay so the frontend has time to set up listeners
-                            std::thread::spawn(move || {
-                                std::thread::sleep(std::time::Duration::from_millis(500));
-                                let _ = win.emit("open-file", path_str);
-                            });
-                        }
-                    }
-                }
-            }
-
             Ok(())
         })
         .on_window_event(|window, event| {