fix(identity): 3 项根因级修复 — Agent ID 映射 + user_profile 读取 + 用户画像 fallback

Issue 2: IdentityFile 枚举补全 UserProfile 变体
- get_file()/propose_change()/approve_proposal() 补全 match arm
- identity_get_file/identity_propose_change Tauri 命令支持 user_profile

Issue 1: Agent ID 映射机制
- 新增 resolveKernelAgentId() 工具函数 (带缓存)
- ButlerPanel 使用 kernel UUID 替代 SaaS relay "1" 查询 VikingStorage

Issue 3: 用户画像 fallback 注入
- build_system_prompt 改为 async，identity user_profile 为默认值时
  从 VikingStorage preferences 路径查询最近 5 条记忆作为 fallback
- intelligence_hooks 调用处同步加 .await

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

desktop/src/lib/kernel-agent.ts

@@ -270,3 +270,42 @@ export function installAgentMethods(ClientClass: { prototype: KernelClient }): v
     return { clone };
   };
 }
+
+// === Agent ID Resolution ===
+
+/**
+ * Cached kernel default agent UUID.
+ * The conversationStore's DEFAULT_AGENT has id="1", but VikingStorage
+ * stores data under kernel UUIDs. This cache bridges the gap.
+ */
+let _cachedDefaultKernelAgentId: string | null = null;
+
+/**
+ * Resolve an agent ID to the kernel's actual agent UUID.
+ * - If already a UUID (8-4-4 hex pattern), return as-is.
+ * - If "1" or undefined, query agent_list and cache the first kernel agent's UUID.
+ * - Falls back to the original ID if kernel has no agents.
+ */
+export async function resolveKernelAgentId(agentId: string | undefined): Promise<string> {
+  if (agentId && /^[0-9a-f]{8}-[0-9a-f]{4}-/.test(agentId)) {
+    return agentId;
+  }
+  if (_cachedDefaultKernelAgentId) {
+    return _cachedDefaultKernelAgentId;
+  }
+  try {
+    const agents = await invoke<{ id: string }[]>('agent_list');
+    if (agents.length > 0) {
+      _cachedDefaultKernelAgentId = agents[0].id;
+      return _cachedDefaultKernelAgentId;
+    }
+  } catch {
+    // Kernel may not be available
+  }
+  return agentId || '1';
+}
+
+/** Invalidate cache when kernel reconnects (new instance may have different UUIDs) */
+export function invalidateKernelAgentIdCache(): void {
+  _cachedDefaultKernelAgentId = null;
+}