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>

src/hooks/useTKMindChat.ts

@@ -48,6 +48,10 @@ import type {
 import { buildContextPrefix } from '../utils/mindspaceChatContext';
 import { buildUserAddressPrefix } from '../utils/userAddress';
 import { buildAutoChatSkillPrefix } from '../../chat-skills.mjs';
+import {
+  resolvePostAgentRunChatState,
+  shouldPromoteSessionIdToStreaming,
+} from '../../chat-agent-run-gate.mjs';
 import { mergeConversationSnapshot } from '../../chat-finish-sync.mjs';
 import {
   CHAT_IMAGE_UPLOAD_MAX_INPUT_BYTES,
@@ -1366,7 +1370,9 @@ export function useTKMindChat(
                   }
                   if (!isDirectChatSessionId(sessionId)) {
                     subscribeToSession(sessionId);
-                    setChatState('streaming');
+                    if (shouldPromoteSessionIdToStreaming(chatStateRef.current)) {
+                      setChatState('streaming');
+                    }
                   }
                 },
                 onMessages: (snapshotMessages) => {
@@ -1443,7 +1449,11 @@ export function useTKMindChat(
             // Fall through to agent streaming when the snapshot is not ready yet.
           }
           subscribeToSession(activeSessionId);
-          if (finishedViaPortalDirectChat) {
+          const nextChatState = resolvePostAgentRunChatState({
+            chatState: chatStateRef.current,
+            finishedViaPortalDirectChat,
+          });
+          if (nextChatState === 'idle') {
             clearActiveRequestMissingTimer();
             activeRequestId.current = null;
             setChatState('idle');