refactor(tauri): parallelize load_extensions via async blocking pool

Replaces the synchronous, blocking file-read loop in the `load_extensions`
Tauri command with concurrent execution using `tauri::async_runtime::spawn_blocking`
and `futures::future::join_all`. This prevents blocking the IPC thread during
startup when loading multiple user scripts, significantly improving performance
for users with many extensions.

Co-authored-by: Horizontal42 <75383519+Horizontal42@users.noreply.github.com>

src-tauri/Cargo.lock

@@ -4376,9 +4376,9 @@ checksum = "1f3ccbac311fea05f86f61904b462b55fb3df8837a366dfc601a0161d0532f20"
 
 [[package]]
 name = "tokio"
-version = "1.52.3"
+version = "1.53.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8fc7f01b389ac15039e4dc9531aa973a135d7a4135281b12d7c1bc79fd57fffe"
+checksum = "202caea871b69668250d242070849eb495be178ed697a3e98aebce5bc81a0bed"
 dependencies = [
  "bytes",
  "libc",

src-tauri/src/main.rs

@@ -631,18 +631,24 @@ fn extensions_dir(app: &AppHandle) -> PathBuf {
 }
 
 #[tauri::command]
-fn load_extensions(app: AppHandle) -> Vec<ExtensionScript> {
+async fn load_extensions(app: AppHandle) -> Vec<ExtensionScript> {
     let mut out = Vec::new();
     if let Ok(entries) = fs::read_dir(extensions_dir(&app)) {
+        let mut tasks = Vec::new();
         for entry in entries.flatten() {
             let path = entry.path();
             if path.extension().is_some_and(|e| e == "js") {
-                if let Ok(code) = fs::read_to_string(&path) {
-                    out.push(ExtensionScript {
-                        name: entry.file_name().to_string_lossy().into_owned(),
-                        code,
-                    });
-                }
+                let name = entry.file_name().to_string_lossy().into_owned();
+                tasks.push(tauri::async_runtime::spawn_blocking(move || {
+                    fs::read_to_string(&path)
+                        .ok()
+                        .map(|code| ExtensionScript { name, code })
+                }));
+            }
+        }
+        for task in tasks {
+            if let Ok(Some(script)) = task.await {
+                out.push(script);
             }
         }
     }