Fix AGENTS.md sccache

[connortsui20]

Summary

The agents keep running cargo commands with RUSTC_WRAPPER= even locally.

Also, this capitalizes the list items because it was annoying me.

Testing

N/A

[codspeed-hq]

Merging this PR will improve performance by 11.04%

⚡ 1 improved benchmark
✅ 1121 untouched benchmarks
⏩ 1455 skipped benchmarks¹

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
⚡	Simulation	take_map[(0.1, 1.0)]	1.8 ms	1.6 ms	+11.04%

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_{Comparing ct/rustc-wrapper (2db8044) with develop (256a029)}

Footnotes

1. 1455 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. ↩