refactor(cat): use raw io

[xtqqczze]

Introduce safe wrappers for raw stdio backed by ManuallyDrop<File>. The ManuallyDrop prevents the file descriptor from being closed on drop, which could otherwise lead to undefined behavior.

The wrapper only exposes &File, so safe code cannot take ownership and accidentally drop the underlying descriptor.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/resolution (passes in this run but fails in the 'main' branch)

[codspeed]

Merging this PR will improve performance by 30.08%

⚡ 2 improved benchmarks
✅ 387 untouched benchmarks
⏩ 54 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	three_39_bit_primes	467.5 ms	287.9 ms	+62.38%
⚡	Simulation	five_38_bit_primes	1.8 s	1.8 s	+4.21%

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 xtqqczze:dd-stdin-raw (dd8a17a) with main (a6d1eb3)}

Footnotes

1. 54 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. ↩