feat(context): 添加上下文压缩 API 和 UI 组件

Server API:
- 扩展 Agent Adapter 接口添加压缩相关方法
- 新增 context.ts 路由 (GET /sessions/:id/context, POST /sessions/:id/compress)
- 扩展 config.ts 添加摘要模型配置接口 (GET/PUT /config/summary)

UI 组件:
- 新增 ContextUsage 组件显示上下文使用情况
- 扩展 ConfigPanel 添加摘要模型配置区域
- 添加 API 客户端方法和类型定义

Web 集成:
- 在 Chat 页面头部集成 ContextUsage 紧凑模式显示

packages/server/src/routes/context.ts

@@ -0,0 +1,106 @@
+/**
+ * Context API Routes
+ *
+ * 上下文压缩相关的 REST API
+ */
+
+import { Hono } from 'hono';
+import { getSessionManager } from '../session/manager.js';
+import {
+  getContextUsage,
+  compressContext,
+  type ContextUsageInfo,
+  type CompressionResult,
+} from '../agent/adapter.js';
+
+export const contextRouter = new Hono();
+
+/**
+ * GET /sessions/:id/context - 获取会话上下文使用情况
+ */
+contextRouter.get('/sessions/:id/context', (c) => {
+  const sessionId = c.req.param('id');
+  const sessionManager = getSessionManager();
+
+  // 验证会话存在
+  if (!sessionManager.exists(sessionId)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  const usage = getContextUsage(sessionId);
+
+  if (!usage) {
+    // Agent 未初始化，返回默认值
+    return c.json({
+      success: true,
+      data: {
+        input: 0,
+        contextLimit: 200000,
+        available: 180000,
+        usagePercent: 0,
+        formatted: '0/180K (0%)',
+        shouldCompress: false,
+      } as ContextUsageInfo,
+    });
+  }
+
+  return c.json({
+    success: true,
+    data: usage,
+  });
+});
+
+/**
+ * POST /sessions/:id/compress - 触发手动压缩
+ */
+contextRouter.post('/sessions/:id/compress', async (c) => {
+  const sessionId = c.req.param('id');
+  const sessionManager = getSessionManager();
+
+  // 验证会话存在
+  if (!sessionManager.exists(sessionId)) {
+    return c.json(
+      {
+        success: false,
+        error: 'Session not found',
+      },
+      404
+    );
+  }
+
+  try {
+    const body = await c.req.json().catch(() => ({}));
+    const force = body.force === true;
+
+    const result = await compressContext(sessionId, force);
+
+    if (!result) {
+      return c.json(
+        {
+          success: false,
+          error: 'Agent not initialized for this session',
+        },
+        400
+      );
+    }
+
+    return c.json({
+      success: true,
+      data: result,
+    });
+  } catch (error) {
+    return c.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : 'Compression failed',
+      },
+      500
+    );
+  }
+});