trade_seq was missing from the kernel account snapshot dict, so the
intent engine always computed trade_id = "BTCUSDT-T-000000000001".
The Rust FSM SLOT_BUSY guard only fires on *different* trade_ids; with
the same ID it resets the slot and submits a new exchange order on each
ENTER signal tick (~86 duplicate orders observed in one session).
Fix:
- Add _slot_was_closed dict to ExecutionKernel; set False on ENTER
accepted (both sync/async), True on on_venue_event when slot.closed
- Increment account.snapshot.trade_seq on the IDLE→CLOSED transition
- Expose trade_seq in snapshot()["account"] so DecisionContext carries
the correct counter → intent engine generates unique IDs per trade
451/451 tests green.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>