feat(task-watcher): heartbeat 발신 (state=mode, paused 이유 노출)

- watcher_loop 에서 mode 판정 직후 worker:task-watcher:heartbeat SET EX 45
- payload: build_payload(state=mode, extra={"mode": mode})
- LOOP_INTERVAL 30s < TTL 45s → 만료 전 주기적 갱신
- conftest.py 추가: services/ 를 sys.path에 주입해 _shared import 가능
- tests/test_watcher.py: payload kind/state/mode 필드 검증 (1 passed)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

services/task-watcher/conftest.py

@@ -0,0 +1,5 @@
+"""Make services/ root importable so `from _shared.heartbeat import ...` works during tests."""
+import sys
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))

services/task-watcher/tests/test_watcher.py

@@ -0,0 +1,16 @@
+"""task-watcher heartbeat payload — state=mode + mode 필드 검증."""
+import json
+
+from _shared.heartbeat import build_payload, WorkerStats
+
+
+def test_watcher_heartbeat_payload_carries_mode():
+    payload = json.loads(
+        build_payload(
+            "task-watcher", "watcher", "trading",
+            WorkerStats(), extra={"mode": "trading"},
+        )
+    )
+    assert payload["kind"] == "watcher"
+    assert payload["state"] == "trading"
+    assert payload["mode"] == "trading"

services/task-watcher/watcher.py

@@ -15,6 +15,7 @@ from zoneinfo import ZoneInfo
 import redis.asyncio as aioredis
 
 from mode import current_mode, fetch_holidays, KST
+from _shared.heartbeat import build_payload, WorkerStats
 
 logger = logging.getLogger(__name__)
 
@@ -23,6 +24,10 @@ PAUSED_KEY = "queue:paused"
 LOOP_INTERVAL = 30          # 초
 HOLIDAYS_REFRESH = 3600     # 1시간
 PAUSED_TTL = 600            # 10분 (watcher 죽어도 자동 해제)
+HEARTBEAT_KEY = "worker:task-watcher:heartbeat"
+HEARTBEAT_TTL = 45          # LOOP_INTERVAL 30s < TTL 45s → 만료 전 갱신
+
+_HB_STATS = WorkerStats()
 
 
 async def watcher_loop():
@@ -46,6 +51,13 @@ async def watcher_loop():
             else:
                 await redis.delete(PAUSED_KEY)
 
+            # heartbeat (LOOP_INTERVAL=30s < TTL 45s → 만료 전 갱신)
+            await redis.set(
+                HEARTBEAT_KEY,
+                build_payload("task-watcher", "watcher", mode, _HB_STATS, extra={"mode": mode}),
+                ex=HEARTBEAT_TTL,
+            )
+
             if mode != last_mode:
                 logger.info("mode 전환: %s → %s (paused=%s)", last_mode, mode, mode == "trading")
                 last_mode = mode