`_calculate_state`, the `use_state_after` roll-back over state deltas of
the full-state path, and the delta loop of the incremental path. The
database reads that produce their inputs stay with the store.
The two Python loops were inline in the handler; they are now functions,
`_roll_back_state_over_deltas` and `_apply_current_state_deltas`, so that
`tests/sync/test_rust_state_delta.py` can compare them with the Rust on
random state maps and deltas. Behaviour is unchanged.
One deliberate difference: when the start and end of the timeline
disagree on a key that is in neither the timeline nor the previous state,
`_calculate_state` sends whichever event its set iteration visits last.
The Rust sends the one from the end of the timeline, the state the client
should end up with. The test allows the Python either.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0194eNQP5weBtVMg8NKtc6VU
