chore: standardize rustfmt config

[Boshen]

Standardizes the Rustfmt config filename and options, then applies cargo fmt.

[codspeed-hq]

Merging this PR will degrade performance by 1.34%

❌ 1 regressed benchmark
✅ 11 untouched benchmarks

Warning

Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
❌	swc[parallel]	86.2 ms	87.4 ms	-1.34%

Tip

Investigate this regression by commenting @codspeedbot fix this regression on this PR, or directly use the CodSpeed MCP with your agent.

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_{Comparing codex/standardize-rustfmt-config (a15d6df) with main (175cb13)}