feat: LLM intent router, direct chat execution, and Memory V2 light intervention

Wire chat intent routing with direct_chat on regular sessions, skill-selected
short-circuit to Agent, memory light/heavy intervention tiers, and fix direct
chat UI stuck streaming after completion.

Co-authored-by: Cursor <cursoragent@cursor.com>

direct-chat-service.test.mjs

@@ -6,16 +6,17 @@ import {
   sendDirectChatSessionEvents,
 } from './direct-chat-service.mjs';
 
-test('direct chat is disabled by default', () => {
+test('direct chat is enabled by default', () => {
   const service = createDirectChatService({
     userAuth: {},
     llmProviderService: {},
     sessionSnapshotService: {},
   });
-  assert.equal(service.getStatus().enabled, false);
+  assert.equal(service.getStatus().enabled, true);
   assert.equal(service.canHandle({
     userMessage: { role: 'user', content: [{ type: 'text', text: 'hi' }] },
-  }), false);
+    routingDecision: 'direct_chat',
+  }), true);
 });
 
 test('direct chat creates a direct session, saves snapshot, and bills returned usage', async () => {
@@ -80,9 +81,9 @@ test('direct chat creates a direct session, saves snapshot, and bills returned u
   assert.deepEqual(registered, [
     { userId: 'user-1', sessionId: result.sessionId, target: 'h5-direct' },
   ]);
-  assert.equal(saved.length, 1);
-  assert.equal(saved[0].messages.length, 2);
-  assert.equal(saved[0].messages[1].content[0].text, '你好，已收到。');
+  assert.equal(saved.length, 2);
+  assert.equal(saved[1].messages.length, 2);
+  assert.equal(saved[1].messages[1].content[0].text, '你好，已收到。');
   assert.match(llmMessages[0][0].content, /喜欢简洁回答/);
   assert.deepEqual(billed, [{
     userId: 'user-1',
@@ -201,3 +202,86 @@ test('direct chat rejects page generation tasks so the execution backend can han
     },
   }), false);
 });
+
+test('direct chat allows llm-routed replies on regular agent sessions', () => {
+  const service = createDirectChatService({
+    enabled: true,
+    userAuth: {},
+    llmProviderService: {},
+    sessionSnapshotService: {},
+  });
+  const userMessage = {
+    role: 'user',
+    content: [{ type: 'text', text: '我想对太湖有更多的了解' }],
+    metadata: { displayText: '我想对太湖有更多的了解' },
+  };
+  assert.equal(service.canHandle({
+    sessionId: '20260704_11',
+    routingDecision: 'direct_chat',
+    userMessage,
+  }), true);
+  assert.equal(service.explainCanHandle({
+    sessionId: '20260704_11',
+    routingDecision: 'direct_chat',
+    userMessage,
+  }).reason, null);
+});
+
+test('direct chat run saves portal reply into an existing agent session', async () => {
+  const saved = [];
+  const service = createDirectChatService({
+    enabled: true,
+    userAuth: {
+      async getBillingState() {
+        return null;
+      },
+      async billSessionUsage() {
+        return null;
+      },
+    },
+    llmProviderService: {
+      async createChatCompletion() {
+        return {
+          ok: true,
+          model: 'deepseek-chat',
+          reply: '太湖是中国第三大淡水湖。',
+          usage: null,
+        };
+      },
+    },
+    sessionSnapshotService: {
+      async get(sessionId) {
+        return {
+          session: { id: sessionId, name: 'New Chat', updated_at: '2026-07-04T00:00:00.000Z' },
+          messages: [{
+            id: 'user-1',
+            role: 'user',
+            content: [{ type: 'text', text: 'hi' }],
+            metadata: { userVisible: true },
+          }],
+        };
+      },
+      async save(sessionId, userId, session, messages) {
+        saved.push({ sessionId, userId, session, messages });
+      },
+    },
+  });
+
+  const result = await service.run({
+    userId: 'user-1',
+    sessionId: '20260704_11',
+    requestId: 'req-taihu',
+    routingDecision: 'direct_chat',
+    userMessage: {
+      id: 'user-taihu',
+      role: 'user',
+      content: [{ type: 'text', text: '我想对太湖有更多的了解' }],
+      metadata: { displayText: '我想对太湖有更多的了解', userVisible: true },
+    },
+  });
+
+  assert.equal(result.sessionId, '20260704_11');
+  assert.equal(saved.length, 2);
+  assert.equal(saved[1].messages.at(-1)?.metadata?.source, 'portal-direct-chat');
+  assert.match(saved[1].messages.at(-1)?.content?.[0]?.text ?? '', /太湖/);
+});