feat(h5): web 联网能力、实时查询路由与 session Finish 对齐

- 新增 web 能力并挂载 platform/web（web_search/fetch_url）
- 实时查询强制 web skill，router fallback 与 await session Finish
- Session Broker 覆盖率/指标、stream replay 与相关单测/E2E 脚本

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

session-stream.mjs

@@ -0,0 +1,56 @@
+export const SESSION_STREAM_TERMINAL_TYPES = new Set(['Finish', 'Error']);
+
+function envFlag(value, fallback = false) {
+  const raw = String(value ?? '').trim().toLowerCase();
+  if (!raw) return fallback;
+  return ['1', 'true', 'yes', 'on'].includes(raw);
+}
+
+export function isSessionStreamReplayEnabled(env = process.env) {
+  return envFlag(env.MEMIND_SESSION_STREAM_REPLAY, false);
+}
+
+export function parseSessionStreamLastEventId(value) {
+  const id = String(value ?? '').trim();
+  return id || null;
+}
+
+export function isTerminalSessionEvent(event) {
+  const type = String(event?.type ?? '').trim();
+  return SESSION_STREAM_TERMINAL_TYPES.has(type);
+}
+
+export function shouldPersistSessionStreamEvent(event) {
+  const type = String(event?.type ?? '').trim();
+  if (!type) return false;
+  return type !== 'Ping';
+}
+
+export function parseSessionSseBlock(block) {
+  const lines = String(block ?? '').split('\n');
+  let id = null;
+  let eventName = null;
+  let data = null;
+  for (const line of lines) {
+    if (line.startsWith('id:')) id = line.slice(3).trim() || null;
+    if (line.startsWith('event:')) eventName = line.slice(6).trim() || null;
+    if (line.startsWith('data:')) data = line.slice(5).trim();
+  }
+  return { id, eventName, data };
+}
+
+export function formatSessionStreamSseChunk({ id = null, event = null, data }) {
+  const lines = [];
+  if (id) lines.push(`id: ${id}`);
+  if (event) lines.push(`event: ${event}`);
+  lines.push(`data: ${JSON.stringify(data)}`);
+  return `${lines.join('\n')}\n\n`;
+}
+
+export function shouldSkipUpstreamAfterSessionReplay(events, { cursorMiss = false } = {}) {
+  if (!Array.isArray(events) || events.length === 0) {
+    return cursorMiss ? false : false;
+  }
+  const last = events[events.length - 1];
+  return isTerminalSessionEvent(last?.payload ?? last);
+}