fix(error): add global error handler, fix stores and dispatcher

- Global unhandledrejection handler with IPC+network filtering
- Agent dispatcher heartbeat uses handleInfraError (was fire-and-forget)
- All stores: layout, workspace, anchors, theme, plugins, machines,
  wake-scheduler — silent failures replaced with handleInfraError
- initGlobalErrorHandler() called in App.svelte onMount

src/lib/stores/plugins.svelte.ts

@@ -7,6 +7,7 @@ import type { PluginMeta } from '../adapters/plugins-bridge';
 import { discoverPlugins } from '../adapters/plugins-bridge';
 import { getSetting, setSetting } from '../adapters/settings-bridge';
 import { loadPlugin, unloadPlugin, unloadAllPlugins, getLoadedPlugins } from '../plugins/plugin-host';
+import { handleInfraError } from '../utils/handle-error';
 import type { GroupId, AgentId } from '../types/ids';
 
 // --- Plugin command registry (for CommandPalette) ---
@@ -65,7 +66,7 @@ class PluginEventBusImpl {
       try {
         cb(data);
       } catch (e) {
-        console.error(`Plugin event handler error for '${event}':`, e);
+        handleInfraError(e, `plugins.eventHandler(${event})`);
       }
     }
   }
@@ -140,7 +141,7 @@ async function loadSinglePlugin(
     );
   } catch (e) {
     const errorMsg = e instanceof Error ? e.message : String(e);
-    console.error(`Failed to load plugin '${entry.meta.id}':`, errorMsg);
+    handleInfraError(e, `plugins.loadPlugin(${entry.meta.id})`);
     pluginEntries = pluginEntries.map(e =>
       e.meta.id === entry.meta.id ? { ...e, status: 'error' as PluginStatus, error: errorMsg } : e,
     );
@@ -161,7 +162,7 @@ export async function loadAllPlugins(groupId?: GroupId, agentId?: AgentId): Prom
   try {
     discovered = await discoverPlugins();
   } catch (e) {
-    console.error('Failed to discover plugins:', e);
+    handleInfraError(e, 'plugins.discover');
     pluginEntries = [];
     return;
   }