feat: bf16 support

[justventure]

Summary

Added support bf16 data type via half #315

Checklist

Delete items not relevant to your PR:

• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided so that we can include it in CHANGELOG later

[Copilot]

Pull request overview

Adds ClickHouse BFloat16 (brain floating point 16-bit) support to the crate’s bespoke types module and teaches the RowBinary (de)serializer + schema validator to treat it as a fixed-size 2-byte value, with integration/unit tests to validate round-trips and Nullable behavior.

Changes:

• Introduce types::BFloat16 with RowBinary-focused serde (de)serialization.
• Extend RowBinary serializer/deserializer and schema validation to recognize BFloat16 as fixed 2-byte data.
• Add integration test coverage for inserting/selecting BFloat16 and Nullable(BFloat16).

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/it/main.rs	Registers the new bfloat16 integration test module.
tests/it/bfloat16.rs	End-to-end integration test for BFloat16 and Nullable(BFloat16) behavior.
src/types/mod.rs	Re-exports BFloat16 and wires the new bf16 module into types.
src/types/bf16.rs	Implements the BFloat16 type, conversions, constants, and serde encoding for RowBinary.
src/rowbinary/validation.rs	Allows SerdeType::Bytes(2) to match ClickHouse BFloat16 during schema validation.
src/rowbinary/ser.rs	Treats BFloat16 as fixed-size bytes (no length prefix) during RowBinary serialization.
src/rowbinary/de.rs	Treats BFloat16 as fixed-size bytes during RowBinary deserialization.
Cargo.toml	Adds the half crate dependency used for conversions.

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[abonander]

Surprisingly this time around, I agree with the Copilot review comments.

[abonander]

@justventure do you have time to address the review comments?

[abonander]

Just a couple nits, plus rustfmt needs to be run.

[justventure]

i was away for approximately one month due to travel, sorry for delay