feat(swarm): add in-process agent spawning with live auction bidding

- Add spawn_in_process_agent() to SwarmCoordinator: creates lightweight
  SwarmNode instances that share the coordinator's comms layer and
  AuctionManager, enabling synchronous bid submission
- Fix post_task() to open the auction BEFORE announcing via comms so
  in-process agent callbacks can submit bids into an open auction
- Fix run_auction_and_assign() to close an already-open auction instead
  of re-opening (which would discard bids)
- Add POST /swarm/tasks/auction route for atomic task+auction flow
- Add 7 integration tests (TDD) covering the full lifecycle:
  spawn → post → auction → assign → complete

src/dashboard/routes/swarm.py

@@ -88,6 +88,21 @@ async def post_task(description: str = Form(...)):
     }
 
 
+@router.post("/tasks/auction")
+async def post_task_and_auction(description: str = Form(...)):
+    """Post a task and immediately run an auction to assign it."""
+    task = coordinator.post_task(description)
+    winner = await coordinator.run_auction_and_assign(task.id)
+    updated = coordinator.get_task(task.id)
+    return {
+        "task_id": task.id,
+        "description": task.description,
+        "status": updated.status.value if updated else task.status.value,
+        "assigned_agent": updated.assigned_agent if updated else None,
+        "winning_bid": winner.bid_sats if winner else None,
+    }
+
+
 @router.get("/tasks/{task_id}")
 async def get_task(task_id: str):
     """Get details for a specific task."""