Docs: clear up safety documentation

[connortsui20]

Removes an incorrect safety doc plus adds an extra comment for the missing width check.

[connortsui20]

This was wrong

[codspeed-hq]

CodSpeed Performance Report

Merging #102 will degrade performances by 23.76%

_{Comparing ct/safety-docs (fb498f7) with develop (81e9c70)}

Summary

⚡ 7 improvements
❌ 7 regressions
✅ 22 untouched
⏩ 16 skipped¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Benchmarks breakdown

	Benchmark	BASE	HEAD	Change
❌	pack_16_to_3_stack	1.7 µs	2.2 µs	-23.76%
❌	unchecked_unpack_16_from_3_stack	2.6 µs	3 µs	-12.68%
❌	unpack_16_from_3_stack	2.5 µs	2.9 µs	-13.22%
⚡	bitpacking_cmp_seq[u16]	5.8 µs	5.2 µs	+10.04%
⚡	bitpacking_cmp_seq[u32]	5.2 µs	4.2 µs	+23.62%
⚡	bitpacking_cmp_seq[u64]	7.5 µs	5.6 µs	+33.7%
⚡	bitpacking_cmp_unpack[u16]	3.1 µs	2.6 µs	+16.55%
⚡	bitpacking_cmp_unpack[u32]	5.2 µs	4.3 µs	+21.07%
⚡	bitpacking_cmp_unpack[u64]	9.5 µs	7.7 µs	+23.85%
⚡	for_pack_16_to_3_stack	2.3 µs	1.8 µs	+29.28%
❌	unchecked_unfor_pack_16_from_3_stack	2.7 µs	3.2 µs	-13.85%
❌	unchecked_unpack_then_add_reference_16_from_3_stack	3.4 µs	3.8 µs	-11.5%
❌	unfor_pack_16_from_3_stack	2.5 µs	3 µs	-14.7%
❌	unpack_then_add_reference_16_from_3_stack	3.2 µs	3.7 µs	-11.98%

Footnotes

1. 16 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. ↩