M1：镜生域后端闭环——灵胚/照心试演/启镜原子闸门/执镜关系/命台租约/魂籍签名导出/死亡冷静期（迁移 001，测试 7 用例）

backend/app/domains/jingsheng/seat.py

@@ -0,0 +1,94 @@
+"""命台租约（authoritative_runtime_seat）：同一人物唯一权威运行位置。
+
+- 活跃租约（未过期、非本人）存在时，其他持有者获取被拒（SeatConflict）；
+- 租约过期可接管，epoch 递增（旧持有者写入按 epoch 失效——M2 运行时接入）；
+- 事件（seat.acquired / released / contested）由 API 层在事务提交后发射，
+  避免事务内跨连接写冲突；M1 为 API 级租约，Kernel 前台串行仍为进程内锁，多进程一致在 M2 收口。
+"""
+
+from __future__ import annotations
+
+from datetime import timedelta
+
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from app.core.time import as_utc, utc_now
+from app.models.jingsheng import RuntimeSeat
+
+
+class SeatConflict(Exception):
+    """命台被其他持有者占用（HJ-1101 语义）；调用方须留痕 seat.contested。"""
+
+    def __init__(self, seat: RuntimeSeat) -> None:
+        super().__init__(f"命台被 {seat.holder} 占用至 {seat.lease_expires_at}")
+        self.seat = seat
+
+
+async def acquire_lease(
+    session: AsyncSession, character_id: str, holder: str, ttl_seconds: int = 60
+) -> RuntimeSeat:
+    """获取或续期命台租约；冲突抛 SeatConflict（不在此发事件，避免事务内跨连接写）。"""
+    seat = await session.scalar(select(RuntimeSeat).where(RuntimeSeat.character_id == character_id))
+    if seat is None:
+        seat = RuntimeSeat(character_id=character_id, epoch=0)
+        session.add(seat)
+    now = utc_now()
+    if (
+        seat.holder is not None
+        and seat.holder != holder
+        and seat.lease_expires_at is not None
+        and as_utc(seat.lease_expires_at) > now
+    ):
+        raise SeatConflict(seat)
+    # 仅"从其他持有者手中接管"递增 epoch；无人持有时首次获取沿用当前纪元
+    takeover = seat.holder is not None and seat.holder != holder
+    seat.holder = holder
+    seat.lease_expires_at = now + timedelta(seconds=ttl_seconds)
+    if takeover:
+        seat.epoch += 1
+    await session.flush()
+    return seat
+
+
+async def release_lease(session: AsyncSession, character_id: str, holder: str) -> bool:
+    """释放租约；返回是否实际释放（holder 不匹配时无操作）。"""
+    seat = await session.scalar(select(RuntimeSeat).where(RuntimeSeat.character_id == character_id))
+    if seat is None or seat.holder != holder:
+        return False
+    seat.holder = None
+    seat.lease_expires_at = None
+    await session.flush()
+    return True
+
+
+async def emit_seat_event(
+    event_type: str,
+    character_id: str,
+    holder: str | None,
+    epoch: int | None,
+    *,
+    requester: str | None = None,
+) -> None:
+    """事务外发射命台事件（一炁，visibility=internal）。"""
+    from app.modules.runtime.events import Event
+    from app.services.event_store import DbEventStore
+
+    from app.domains.jingsheng import service as jingsheng_service
+
+    store: DbEventStore | None = jingsheng_service._event_store  # noqa: SLF001
+    if store is None:
+        return
+    payload: dict = {"holder": holder, "epoch": epoch}
+    if requester is not None:
+        payload["requester"] = requester
+    await store.append(
+        Event(
+            type=event_type,
+            source="jingsheng",
+            payload=payload,
+            visibility="internal",
+            run_id=None,
+            character_id=character_id,
+        )
+    )