docs(test): store Wave 0 SSE evidence as txt (log gitignored)

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

.doc/ops/short-term/2026-09-18-wave0-p0-bug-fixes.md

@@ -52,4 +52,4 @@ mutex: chat + web
 ## 证据 / 备注
 
 - Commits：`64efaa3` docs · `54244ed` server · `2620d80` web；合入 `dev` merge `810fb96`
-- Assets：`.doc/test-reports/assets/2026-09-18-wave0-p0-bug-fixes/chat-stream-long.sse.log`
+- Assets：`.doc/test-reports/assets/2026-09-18-wave0-p0-bug-fixes/chat-stream-long.sse.txt`

.doc/test-reports/2026-09-18-wave0-p0-bug-fixes-test-report.md

@@ -95,7 +95,7 @@ npx tsx --test src/hooks/useChatWindow.cacheKey.test.ts \
 
 ### 5.5 真实 PI 聊天 SSE（心跳接线证据）
 
-**测试输入**：admin 登录后 `POST /api/v1/chat/stream`，长合规分析提示词；资产见 `assets/2026-09-18-wave0-p0-bug-fixes/chat-stream-long.sse.log`
+**测试输入**：admin 登录后 `POST /api/v1/chat/stream`，长合规分析提示词；资产见 `assets/2026-09-18-wave0-p0-bug-fixes/chat-stream-long.sse.txt`
 
 **实际输出（关键片段）**：
 

.doc/test-reports/assets/2026-09-18-wave0-p0-bug-fixes/chat-stream-long.meta.json

@@ -7,6 +7,6 @@
   "error_event": false,
   "agent_backend": "pi-agent",
   "model": "MiniMax-M2.7-highspeed",
-  "log": "chat-stream-long.sse.log",
+  "log": "chat-stream-long.sse.txt",
   "note": "Silent PI generation interval produced 4 heartbeats; stream completed with event:done. Absolute wall-clock >120s covered by TestSSEHeartbeat_HelpersSurviveShortWriteTimeout (same helpers)."
 }