Fix stable Rust chunk lint

[Alek99]

What changed

• Replaced fixed-width chunks_exact / chunks_exact_mut loops with as_chunks / as_chunks_mut in the Rust kernels, raster, and tile paths.
• Preserved each call site's remainder handling and tuple width.

Why

Rust 1.96.1 enables clippy::chunks_exact_to_as_chunks, and the repository promotes warnings to errors. The floating stable CI toolchain therefore rejected the existing loops even though their behavior was correct.

Impact

The required stable-Rust Clippy gate passes again without changing the data-path semantics.

Validation

• cargo clippy --all-targets -- -D warnings
• cargo test — 137 passed

Fixes #392

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Review details

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 6d7f119f-6e13-4d57-9639-9a1ac86676bf

📥 Commits

Reviewing files that changed from the base of the PR and between d505ef5 and 8cf48a1.

📒 Files selected for processing (3)

• src/kernels.rs
• src/raster.rs
• src/tiles.rs

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[codspeed-hq]

Merging this PR will not alter performance

✅ 109 untouched benchmarks
⏩ 2 skipped benchmarks¹

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_{Comparing agent/fix-392-stable-rust-chunks (8cf48a1) with main (d505ef5)}

Footnotes

1. 2 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[cubic-dev-ai]

No issues found across 3 files

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