Fix: register bigint as an 8-byte integer to fix RangeError on bigint columns

[otegami]

The CI has failed about DuckDB since 2026-06-21 as follows.

Error: test_bigint_active_record(TestType): ActiveModel::RangeError:
4294967296 is out of range for ActiveModel::Type::Integer with limit 4 bytes

ref: https://github.com/red-data-tools/activerecord-adbc-adapter/actions/runs/27942838514/job/82680163239?pr=29#step:10:1

Cause

DuckDB 1.5.4 started reporting xdbc_type_name. It was nil in DuckDB 1.5.3,
so no cast type was resolved at all.

ref: duckdb/duckdb#23110

So new_column_from_field now resolves a cast type from xdbc_type_name. We
don't override the type map, so that lookup goes like this.

1. BIGINT matches AbstractAdapter's only integer entry,
   register_class_with_limit m, %r(int)i, Type::Integer.
2. register_class_with_limit takes the limit from extract_limit, which
   only reads digits inside (...).
3. BIGINT has no (...), so the limit is nil and Type::Integer falls
   back to DEFAULT_LIMIT = 4.
4. 4 bytes allows up to 1 << (4 * 8 - 1), so writing 2 ** 32 raises.

PostgreSQL is in the same state for the same reason. Its ADBC driver reports
typ.typname, which is int8 for both bigint and bigserial, and int8
has no (...) either.

SQLite is safe by accident: our DDL emits bigint(8), so step 2 finds the 8.

Fix

Register bigint and int8 as 8 bytes, like PostgreSQLAdapter does for
int8. Both names mean 8 bytes on all three backends. An explicit 'limit:'
still wins, so t.bigint :x, limit: 4 keeps resolving to 4 bytes in SQLite.

[kou]

Why do we need these changes? I think that both of 2 ** 32 and 2 ** 64 are int64 range. (They are out of int32 range.)

[otegami]

I've reverted this change because it was not necessary, as you mentioned.
I changed it because I initially wanted a test value that needed 8 bytes.
But both are out of the int32 range and within the int64 range, so the change was unnecessary.

[kou]

Could you add a comment why we need this?

[otegami]

fix: 3ae5738 I added the comment here.

[otegami]

Thank you for reviewing. I've just addressed all of them.

[kou]

Thanks.