ci: fix MSRV check

[wjones127]

The rust-toolchain.toml file has been making our current MSRV check inert. This environment variable should override it.

Also updates MSRV to 1.88 (same as DataFusion) and makes associated clippy fixes.

[github-actions]

Code Review

P0 - YAML Syntax Error: The env syntax on line 273 is incorrect. GitHub Actions expects env: as a mapping (with a colon and newline), not env: KEY=VALUE on the same line.

The current change:

      - name: cargo +${{ matrix.msrv }} check
        env: RUSTUP_TOOLCHAIN=${{ matrix.msrv }}

Should be:

      - name: cargo +${{ matrix.msrv }} check
        env:
          RUSTUP_TOOLCHAIN: ${{ matrix.msrv }}

The idea to use RUSTUP_TOOLCHAIN instead of rustup default is correct - this environment variable properly overrides the rust-toolchain.toml file. However, the current YAML syntax will cause the workflow to fail to parse.

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The MSRV updates in java/lance-jni/Cargo.toml and python/Cargo.toml (1.80 → 1.82) correctly align with the workspace rust-version = "1.82.0" in the root Cargo.toml.

[westonpace]

This tells it to ignore the toolchain file basically?

[wjones127]

Yeah it's higher up in the resolution chain: https://rust-lang.github.io/rustup/overrides.html

[codecov]

Codecov Report

❌ Patch coverage is 81.25000% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
...ncoding/src/previous/encodings/physical/bitpack.rs	0.00%	2 Missing and 1 partial ⚠️

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