agent: foundation — sync incremental changes from legacy codebase

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

src/lib/pages/SettingsPage.svelte

@@ -100,8 +100,9 @@
       await invoke("download_model", { size });
       downloadedModels = await invoke("list_models");
       downloadingModel = "";
-    } catch {
+    } catch (err) {
       downloadingModel = "";
+      engineStatus = typeof err === "string" ? err : "Download failed";
     }
   }
 
@@ -138,9 +139,9 @@
       parakeetDownloaded = true;
       parakeetDownloading = false;
       parakeetStatus = "Downloaded (not loaded)";
-    } catch {
+    } catch (err) {
       parakeetDownloading = false;
-      parakeetStatus = "Download failed";
+      parakeetStatus = typeof err === "string" ? err : "Download failed";
     }
   }