f2596e1155
Fix 1: connect() — remove redundant _backend_snapshot(include_history=True). backend.connect() already called refresh_state(); this was a second identical network round-trip at startup (~400ms wasted). Fix 2: cancel() — remove snapshot_before + snapshot_after. _events_from_cancel never reads 'before' or 'after' — two gratuitous round-trips per cancel with zero benefit. Fix 3: submit() (sync/legacy path) — drop both _backend_snapshot calls, pass None like submit_async already does. Receipt executedQty fields take precedence; _filled_size_from_snapshots returning 0.0 is the correct safe fallback. 117/117 tests pass (2 pre-existing pytest-ordering failures in TestMockSubscribe are unrelated — asyncio.get_event_loop() contamination from other suite files, 25/25 pass when the file runs alone). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>