feat: 预算警告 & Shadowing 防护 & 记忆容量管理 (v5.1.2)

- 预算警告临时层：Agent Loop 剩余 ≤5 轮注入 WARNING，≤2 轮注入 CRITICAL
- MCP Shadowing 防护：MCP 工具注册时检测重名，自动跳过并警告
- 记忆容量限制：上限 500 条，超限自动清理低价值条目（rule 受保护）
- 版本号更新至 5.1.2

src/renderer/services/agent-engine.ts

@@ -529,6 +529,17 @@ export async function runAgentLoop(
     const toolCalls: ToolCall[] = [];
     allCallsThisLoop = [];
 
+    // v5.1.2 预算警告：接近迭代上限时注入临时提示
+    let budgetWarningIdx = -1;
+    const remaining = maxLoops - loopCount + 1;
+    if (remaining <= 5 && remaining > 0) {
+      const warning = remaining <= 2
+        ? `\n⚠️ CRITICAL: You have only ${remaining} iteration(s) left. Stop using tools and provide your final answer NOW.`
+        : `\n⚠️ WARNING: You have approximately ${remaining} iterations remaining. Start wrapping up and prepare your final answer.`;
+      messages.push({ role: 'system', content: warning });
+      budgetWarningIdx = messages.length - 1;
+    }
+
     const abortController = new AbortController();
     state.set(KEYS.ABORT_CONTROLLER, abortController);
 
@@ -587,6 +598,10 @@ export async function runAgentLoop(
         return;
       }
       logError('流式调用异常', (err as Error).message);
+      // 清理预算警告临时消息
+      if (budgetWarningIdx >= 0) {
+        messages.splice(budgetWarningIdx, 1);
+      }
       if (content || thinking) {
         messages.push({ role: 'assistant', content: content || '（模型响应异常）', ...(thinking && { thinking }) });
       }
@@ -594,6 +609,11 @@ export async function runAgentLoop(
       return;
     }
 
+    // 清理预算警告临时消息
+    if (budgetWarningIdx >= 0) {
+      messages.splice(budgetWarningIdx, 1);
+    }
+
     // 提取 ReAct 思考过程
     const thoughtMatch = content.match(/\*\*Thought:\*\*\s*([\s\S]*?)(?=\*\*Action:\*\*|\*\*Final Answer:\*\*|$)/i);
     const thought = thoughtMatch ? thoughtMatch[1].trim() : '';

src/renderer/services/memory-manager.ts

@@ -255,6 +255,15 @@ export async function addMemory(data: {
     throw new Error(`记忆内容被安全规则拦截: ${securityCheck.reason}`);
   }
 
+  // v5.1.2 记忆容量限制：超过上限自动清理低价值条目
+  const MAX_MEMORIES = 500;
+  if (memoryCache.length >= MAX_MEMORIES) {
+    const evicted = autoCleanMemories();
+    if (evicted > 0) {
+      logInfo('记忆容量清理', `已清理 ${evicted} 条低价值记忆（上限 ${MAX_MEMORIES}）`);
+    }
+  }
+
   // 检查重复（内容相似度 > 80% 则跳过）
   const existing = memoryCache.find(e => {
     if (e.type !== data.type) return false;
@@ -300,6 +309,45 @@ export async function addMemory(data: {
   return entry;
 }
 
+// ── 容量管理 ──
+
+/**
+ * 自动清理低价值记忆条目
+ * 策略：按综合评分排序，清理后 20% 的条目
+ * 评分 = importance * 2 + useCount * 3 + recencyBonus（最近 7 天使用过 +5）
+ * rule 类型记忆受保护不被清理
+ * @returns 清理的条目数
+ */
+function autoCleanMemories(): number {
+  const db = state.get<ChatDB | null>(KEYS.DB);
+  const now = Date.now();
+  const SEVEN_DAYS = 7 * 24 * 3600 * 1000;
+
+  // 计算综合评分
+  const scored = memoryCache
+    .map((entry, idx) => {
+      const recencyBonus = (now - entry.lastUsedAt) < SEVEN_DAYS ? 5 : 0;
+      const score = entry.importance * 2 + entry.useCount * 3 + recencyBonus;
+      return { entry, idx, score };
+    })
+    // rule 类型受保护
+    .filter(s => s.entry.type !== 'rule')
+    .sort((a, b) => a.score - b.score);
+
+  const evictCount = Math.max(1, Math.floor(memoryCache.length * 0.2));
+  const toEvict = scored.slice(0, evictCount);
+
+  // 从缓存和数据库中移除
+  const evictIds = new Set(toEvict.map(s => s.entry.id));
+  for (const id of evictIds) {
+    if (db) db.deleteMemory(id);
+  }
+  memoryCache = memoryCache.filter(e => !evictIds.has(e.id));
+  state.set('memoryEntries', [...memoryCache]);
+
+  return evictIds.size;
+}
+
 // ── 安全扫描 ──
 
 /** 记忆内容安全扫描 */

src/renderer/services/tool-registry.ts

@@ -641,9 +641,20 @@ let _mcpToolCache: ToolDefinition[] = [];
 /** 刷新 MCP 工具缓存（在 MCP 服务器配置变更时调用） */
 export async function refreshMCPTools(): Promise<void> {
   try {
-    _mcpToolCache = await getMCPToolDefinitions();
-    if (_mcpToolCache.length > 0) {
-      logInfo(`MCP 工具已注册: ${_mcpToolCache.length} 个`, _mcpToolCache.map(t => t.function.name).join(', '));
+    const rawTools = await getMCPToolDefinitions();
+    // v5.1.2 Shadowing 防护：MCP 工具不能覆盖内置工具
+    const builtInNames = new Set(TOOL_DEFINITIONS.map(d => d.function.name));
+    const filtered = rawTools.filter(t => {
+      if (builtInNames.has(t.function.name)) {
+        logWarn(`MCP 工具 "${t.function.name}" 与内置工具重名，已跳过`);
+        return false;
+      }
+      return true;
+    });
+    const skipped = rawTools.length - filtered.length;
+    _mcpToolCache = filtered;
+    if (filtered.length > 0) {
+      logInfo(`MCP 工具已注册: ${filtered.length} 个${skipped > 0 ? `（${skipped} 个因重名被跳过）` : ''}`, filtered.map(t => t.function.name).join(', '));
     }
   } catch (err) {
     logError('MCP 工具刷新失败', (err as Error).message);