fix(downloads): harden lifecycle race handling

Audit Assignment 06 lifecycle paths and preserve truthful state across ambiguous Aria2 resume failures. Clean up partial startup listener registration and prevent stale resume workers from leaking or releasing current permits.

src/App.tsx

@@ -243,12 +243,79 @@ function App() {
 
   useEffect(() => {
     let active = true;
+    let cleanupListeners: (() => void) | null = null;
     const initialize = async () => {
+      let unlistenDownload: (() => void) | null = null;
+      let unlistenTerminalState: (() => void) | null = null;
+      let unlistenExtension: (() => void) | null = null;
+      let unlistenDeepLink: (() => void) | null = null;
+      const disposeListeners = () => {
+        invoke('set_extension_frontend_ready', { ready: false }).catch(() => {});
+        unlistenTerminalState?.();
+        unlistenTerminalState = null;
+        unlistenExtension?.();
+        unlistenExtension = null;
+        unlistenDeepLink?.();
+        unlistenDeepLink = null;
+        unlistenDownload?.();
+        unlistenDownload = null;
+      };
+
       try {
+        unlistenDownload = await initDownloadListener();
+        unlistenTerminalState = await listen('download-state', (event) => {
+          if (event.payload.status !== 'completed' && event.payload.status !== 'failed') return;
+          const settings = useSettingsStore.getState();
+          if (event.payload.status === 'completed' && settings.playCompletionSound) {
+            playCompletionChime().catch(error => {
+              console.error('Completion sound failed:', error);
+            });
+          }
+          if (!settings.showNotifications) return;
+
+          const item = useDownloadStore.getState().downloads.find(d => d.id === event.payload.id);
+          const fileName = item?.fileName || 'A file';
+          if (event.payload.status === 'completed') {
+            try {
+              sendNotification({
+                title: 'Download Complete',
+                body: `${fileName} has finished downloading.`
+              });
+            } catch (error) {
+              console.error('Completion notification failed:', error);
+            }
+          } else {
+            try {
+              sendNotification({
+                title: 'Download Failed',
+                body: `${fileName} failed to download.`,
+              });
+            } catch (error) {
+              console.error('Failure notification failed:', error);
+            }
+          }
+        });
+        unlistenExtension = await listen('extension-add-download', (event) => {
+          useDownloadStore.getState().handleExtensionDownload(event.payload).catch(error => {
+            console.error('Failed to handle browser extension download:', error);
+          });
+        });
+        unlistenDeepLink = await listen('deep-link-add-download', (event) => {
+          useDownloadStore.getState().openAddModalWithUrls(event.payload);
+        });
+
+        cleanupListeners = disposeListeners;
+        if (!active) {
+          disposeListeners();
+          cleanupListeners = null;
+          return;
+        }
+
         await initializeDownloadState();
         if (!active) return;
-        setCoreReady(true);
       } catch (error) {
+        disposeListeners();
+        cleanupListeners = null;
         if (!active) return;
         console.error('Failed to initialize Firelink state:', error);
         addToast({
@@ -315,10 +382,18 @@ function App() {
           isActionable: true
         });
       }
+
+      if (!active) return;
+      setCoreReady(true);
+      invoke('set_extension_frontend_ready', { ready: true }).catch(error => {
+        console.error('Failed to activate browser extension integration:', error);
+      });
     };
     void initialize();
     return () => {
       active = false;
+      cleanupListeners?.();
+      cleanupListeners = null;
     };
   }, [addToast]);
 
@@ -604,69 +679,6 @@ function App() {
     }
   }, [theme]);
 
-  useEffect(() => {
-    if (!coreReady) return;
-    let disposed = false;
-    const unlistenDownload = initDownloadListener();
-
-    const unlistenTerminalState = listen('download-state', (event) => {
-      if (event.payload.status !== 'completed' && event.payload.status !== 'failed') return;
-      const settings = useSettingsStore.getState();
-      if (event.payload.status === 'completed' && settings.playCompletionSound) {
-        playCompletionChime().catch(error => {
-          console.error('Completion sound failed:', error);
-        });
-      }
-      if (!settings.showNotifications) return;
-
-      const item = useDownloadStore.getState().downloads.find(d => d.id === event.payload.id);
-      const fileName = item?.fileName || 'A file';
-      if (event.payload.status === 'completed') {
-        try {
-          sendNotification({
-            title: 'Download Complete',
-            body: `${fileName} has finished downloading.`
-          });
-        } catch (error) {
-          console.error('Completion notification failed:', error);
-        }
-      } else {
-        try {
-          sendNotification({
-            title: 'Download Failed',
-            body: `${fileName} failed to download.`,
-          });
-        } catch (error) {
-          console.error('Failure notification failed:', error);
-        }
-      }
-    });
-
-    const unlistenExtension = listen('extension-add-download', (event) => {
-      useDownloadStore.getState().handleExtensionDownload(event.payload).catch(error => {
-        console.error('Failed to handle browser extension download:', error);
-      });
-    });
-    const unlistenDeepLink = listen('deep-link-add-download', (event) => {
-      useDownloadStore.getState().openAddModalWithUrls(event.payload);
-    });
-    Promise.all([unlistenExtension, unlistenDeepLink])
-      .then(() => {
-        if (disposed) return;
-        return invoke('set_extension_frontend_ready', { ready: true });
-      })
-      .catch(error => console.error('Failed to activate browser extension integration:', error));
-
-    return () => {
-      disposed = true;
-      invoke('set_extension_frontend_ready', { ready: false }).catch(() => {});
-      unlistenTerminalState.then(f => f());
-      unlistenExtension.then(f => f());
-      unlistenDeepLink.then(f => f());
-      unlistenDownload.then(f => { if (f) f(); });
-    };
-  }, [coreReady]);
-
   return (
     <div className={`app-shell flex h-screen w-screen overflow-hidden text-text-primary ${
       hasWindowChrome ? 'app-shell--window-chrome' : ''