fix: clone marketplace before auto-installing plugin when manifest not found

When auto-installing a plugin from a marketplace that hasn't been
cloned yet, loadMarketplaceManifest throws because the manifest file
doesn't exist. The empty catch block previously just fell through to
installPlugin, which would fail with the same error.

Now the catch block attempts to clone/update the marketplace before
falling through, so installPlugin can succeed.

Author: lewis617

packages/agent-sdk/src/managers/pluginManager.ts

@@ -138,7 +138,14 @@ export class PluginManager {
                 continue;
               }
             } catch {
-              // Manifest read failed (marketplace not cloned yet?) — fall through to installPlugin
+              // Manifest read failed — marketplace may not be cloned yet, try to clone/update it
+              try {
+                await marketplaceService.updateMarketplace(marketplaceName);
+              } catch (updateError) {
+                logger?.warn(
+                  `Failed to clone/update marketplace ${marketplaceName}: ${updateError instanceof Error ? updateError.message : String(updateError)}`,
+                );
+              }
             }
 
             logger?.info(`Auto-installing missing plugin: ${pluginId}`);