[astroknot-sheep]

Fixes #169

Bit objects can be passed as query parameters with Psycopg 3, but not with Psycopg 2 or pg8000. This adds:

• pgvector/psycopg2/bit.py with a BitAdapter, matching HalfvecAdapter / SparsevecAdapter, registered in register_vector
• a Bit out adapter for pg8000 using to_text(), alongside the existing Vector one

asyncpg is unchanged (asyncpg.BitString per #110).

Tests: test_bit_class for Psycopg 2 and pg8000 (both fail on master). Full suite passes locally (527 passed, Postgres 17), plus mypy and ty check.

Written with AI assistance; I have reviewed and tested the changes.

[chrikrah]

@astroknot-sheep this works on both drivers and brings them in line with Psycopg 3, which already adapts Bit. Reverting both register.py files fails the new tests with the #169 errors, and <~>, = and & resolve against a Bit on both drivers.

# Postgres 17 + pgvector (docker.io/pgvector/pgvector:pg17), CPython 3.12, pgvector imported from the exported tree
$ python -m pytest tests -q -p no:cacheprovider        # head 4764b5b
519 passed, 8 skipped in 29.96s

$ python -m pytest tests/test_psycopg2.py tests/test_pg8000.py -q -p no:cacheprovider -k bit_class   # head, both register.py from e0f3ac3
E       psycopg2.ProgrammingError: can't adapt type 'Bit'
E           pg8000.exceptions.DatabaseError: {... 'M': '"i" is not a valid binary digit', ...}
2 failed, 15 deselected in 0.27s

# probe at head: SELECT '111'::bit(3) <~> p1, '1010'::varbit = p2, p3::bit(3) & '011'::bit(3)
# with p1..p3 = Bit("101"), Bit("1010"), Bit("110")
psycopg2 (1.0, True, '010')
pg8000   [[1.0, True, '010']]

# asyncpg 0.32.0 at head, after register_vector(conn)
SELECT $1::bit(3) -> DataError invalid input for query argument $1: Bit(101) (a bytes-like object is required, not 'Bit')

# not run: mypy, ty

non-blocking: asyncpg has the same gap, since its register_vector sets no codec for bit. I'd keep this PR to the two drivers #169 names and track asyncpg in its own issue. Shall I open it?