feat(h5-session): Session Broker、run SSE replay 与 Finish 竞态修复

落地 H5 Session 架构 Patch 1–5（Broker 收口、Router decision、SSE taxonomy、goosed 边界检查），
并新增可选 MEMIND_RUN_STREAM_REPLAY run 事件回放与 H5 假交付 guard；修复 Finish 先于 agent-run
gate 导致 UI 永久 loading 的竞态，接入 verify:h5-session-patches 回归脚本。

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

agent-run-routes.test.mjs

@@ -464,6 +464,40 @@ test('POST /agent/runs rejects a session the user does not own', async () => {
   assert.deepEqual(res.body, { message: '无权访问该会话' });
 });
 
+test('POST /agent/runs validates ownership through sessionAccess when provided', async () => {
+  const validated = [];
+  const handler = createPostAgentRunsHandler({
+    userAuth: {},
+    sessionAccess: {
+      async validateOwnership(userId, sessionId) {
+        validated.push({ userId, sessionId });
+        return false;
+      },
+    },
+    agentRunGateway: {
+      async createRun() {
+        throw new Error('should not be called');
+      },
+    },
+  });
+  const res = createResponseRecorder();
+
+  await handler(
+    {
+      currentUser: { id: 'user-1' },
+      body: {
+        session_id: 'session-broker',
+        request_id: 'req-broker',
+        user_message: { role: 'user', content: [] },
+      },
+    },
+    res,
+  );
+
+  assert.deepEqual(validated, [{ userId: 'user-1', sessionId: 'session-broker' }]);
+  assert.equal(res.statusCode, 403);
+});
+
 test('GET /agent/runs/:runId dispatches unfinished runs', async () => {
   const dispatched = [];
   const handler = createGetAgentRunHandler({
@@ -550,6 +584,94 @@ test('GET /agent/runs/:runId/events streams the current run and closes on termin
   assert.equal(res.ended, true);
 });
 
+test('GET /agent/runs/:runId/events attaches run taxonomy when flag enabled', async () => {
+  const previous = process.env.MEMIND_SSE_EVENT_TAXONOMY;
+  process.env.MEMIND_SSE_EVENT_TAXONOMY = '1';
+  try {
+    const handler = createAgentRunEventsHandler({
+      agentRunGateway: {
+        async getRunForUser() {
+          return { id: 'run-tax', status: 'succeeded', sessionId: 'session-1' };
+        },
+        dispatchRun() {},
+      },
+      pollIntervalMs: 5,
+      keepaliveIntervalMs: 50,
+    });
+    const res = createSseResponseRecorder();
+    await handler(
+      {
+        currentUser: { id: 'user-1' },
+        params: { runId: 'run-tax' },
+        on() {},
+      },
+      res,
+    );
+    assert.match(res.chunks.join(''), /"taxonomy":"terminal"/);
+  } finally {
+    if (previous == null) delete process.env.MEMIND_SSE_EVENT_TAXONOMY;
+    else process.env.MEMIND_SSE_EVENT_TAXONOMY = previous;
+  }
+});
+
+test('GET /agent/runs/:runId/events replay mode emits SSE ids and replays after Last-Event-ID', async () => {
+  const events = [
+    {
+      id: 'evt-1',
+      eventType: 'run_snapshot',
+      data: { run: { id: 'run-replay', status: 'running', sessionId: null } },
+      createdAt: 1,
+    },
+    {
+      id: 'evt-2',
+      eventType: 'run_snapshot',
+      data: { run: { id: 'run-replay', status: 'succeeded', sessionId: 'session-9' } },
+      createdAt: 2,
+    },
+  ];
+  const handler = createAgentRunEventsHandler({
+    replayEnabled: true,
+    agentRunGateway: {
+      async getRunForUser() {
+        return { id: 'run-replay', status: 'succeeded', sessionId: 'session-9' };
+      },
+      async listRunEventsForUser(_userId, _runId, { afterEventId } = {}) {
+        if (afterEventId === 'evt-1') {
+          return {
+            run: { id: 'run-replay', status: 'succeeded', sessionId: 'session-9' },
+            events: [events[1]],
+            cursorMiss: false,
+          };
+        }
+        return {
+          run: { id: 'run-replay', status: 'running', sessionId: null },
+          events,
+          cursorMiss: false,
+        };
+      },
+      dispatchRun() {},
+    },
+    pollIntervalMs: 1000,
+    keepaliveIntervalMs: 5000,
+  });
+  const res = createSseResponseRecorder();
+  await handler(
+    {
+      currentUser: { id: 'user-1' },
+      params: { runId: 'run-replay' },
+      get(name) {
+        return name.toLowerCase() === 'last-event-id' ? 'evt-1' : undefined;
+      },
+      on() {},
+    },
+    res,
+  );
+  assert.equal(res.ended, true);
+  const output = res.chunks.join('');
+  assert.match(output, /id: evt-2/);
+  assert.match(output, /"sessionId":"session-9"/);
+});
+
 test('GET /agent/runs/:runId/events republishes changed run state before terminal close', async () => {
   let readCount = 0;
   const dispatched = [];