Reconcile API streams from State

[AlexCheema]

Why

The API was still closing active streams by reacting directly to InstanceDeleted. That violates the event-sourcing boundary: after snapshot bootstrap, the API may receive State that already reflects a deleted instance without replaying the deletion event.

How

• Remove the API InstanceDeleted side-effect path.
• Add a reconciliation loop that compares active stream queues against generation tasks in State.
• Close queues for commands that were observed in State and are no longer live.
• Preserve a guard for newly sent commands whose TaskCreated has not reached State yet, so the reconciler does not prematurely close fresh requests.
• Update stream-cleanup tests around State reconciliation rather than event reaction.

Tests

• uv run pytest src/exo/api/tests/test_instance_deleted_stream_cleanup.py
• uv run pytest
• uv run ruff check src/exo/api/main.py src/exo/api/tests/test_instance_deleted_stream_cleanup.py
• uv run basedpyright
• nix fmt