ci: reject implicit engine buffer allocation

[gatesn]

Summary

Reject implicit buffer allocation in engine code.

Changes

• Add a check for implicit constructors in allocator-aware paths.
• Run the check in Rust lint CI.

[codspeed-hq]

Merging this PR will improve performance by 51.2%

⚠️ Unknown Walltime execution environment detected

Using the Walltime instrument on standard Hosted Runners will lead to inconsistent data.

For the most accurate results, we recommend using CodSpeed Macro Runners: bare-metal machines fine-tuned for performance measurement consistency.

⚡ 1 improved benchmark
✅ 2089 untouched benchmarks
⏩ 206 skipped benchmarks¹
🗄️ 4 archived benchmarks run²

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	WallTime	arrow_checked_add_u32_neon[16384]	20.4 µs	13.5 µs	+51.2%

Tip

Curious why performance improved? Comment @codspeedbot explain why performance improved on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing ngates/buffer-allocator-enforce (7976d61) with ngates/buffer-allocator-execution (cd00ce3)}

Footnotes

1. 206 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. ↩

2. 4 benchmarks were run, but are now archived. If they were deleted in another branch, consider rebasing to remove them from the report. Instead if they were added back, click here to restore them. ↩