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>

chat-agent-run-gate.test.mjs

@@ -0,0 +1,31 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import {
+  resolvePostAgentRunChatState,
+  shouldPromoteSessionIdToStreaming,
+} from './chat-agent-run-gate.mjs';
+
+test('resolvePostAgentRunChatState keeps idle when Finish beat agent-run gate', () => {
+  assert.equal(
+    resolvePostAgentRunChatState({ chatState: 'idle', finishedViaPortalDirectChat: false }),
+    'idle',
+  );
+});
+
+test('resolvePostAgentRunChatState returns streaming while still waiting for session Finish', () => {
+  assert.equal(resolvePostAgentRunChatState({ chatState: 'waiting' }), 'streaming');
+  assert.equal(resolvePostAgentRunChatState({ chatState: 'streaming' }), 'streaming');
+});
+
+test('resolvePostAgentRunChatState prefers portal direct chat completion', () => {
+  assert.equal(
+    resolvePostAgentRunChatState({ chatState: 'streaming', finishedViaPortalDirectChat: true }),
+    'idle',
+  );
+});
+
+test('shouldPromoteSessionIdToStreaming skips re-streaming after Finish', () => {
+  assert.equal(shouldPromoteSessionIdToStreaming('idle'), false);
+  assert.equal(shouldPromoteSessionIdToStreaming('waiting'), true);
+  assert.equal(shouldPromoteSessionIdToStreaming('streaming'), true);
+});