The first of the pure parts of `/sync` that the Rust sync handler needs:
`RoomStreamToken` with its three string forms and its vector clock
arithmetic (`is_before_or_eq`, `copy_and_advance`, `bound_stream_token`),
`persisted_after`, and the pagination helpers of `stream.py` that turn
tokens into bounds and filter the rows that come back by writer. The SQL
is built in the Postgres row-comparison form only, as the handler reads
through the native Postgres driver.
Tokens cross the boundary as the Python class, converted both ways.
The multi-writer filtering is where a bug would be silent, so
`tests/sync/test_rust_stream_token.py` checks every operation against the
Python on random tokens with instance maps. `tests/sync/fixtures.py`
holds what the differential tests that follow share.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0194eNQP5weBtVMg8NKtc6VU