Restore Rust 1.88 CPUID compatibility

[rob-p]

Finding

The v0.1.0 tag validation exposed that Rust 1.88 declares std::arch::x86_64::{__cpuid,__cpuid_count} unsafe, while current stable declares them safe. This made the published crate build on stable but contradicted its declared MSRV.

Correction

• Route CPUID calls through two narrowly scoped, safety-documented wrappers.
• Retain the unsafe block required by 1.88 while locally allowing only unused_unsafe on newer compilers.
• Record the finding and release disposition in planning/FIRST_RELEASE_REVIEW_REPORT.md and CHANGELOG.md.

Gates

• cargo +1.88.0 check --locked --all-targets: pass
• current-stable build provenance tests: pass
• current-stable warning-denied Clippy for lib/bins/tests: pass
• cargo fmt --all --check and git diff --check: pass

This prepares a possible seqproc 0.1.1 patch. It does not change ANTISEQUENCE and does not itself publish a crate.