ci: establish Phase 0 evidence baseline

[Lord1Egypt]

Summary

• replace one-shot benchmarks with verified repeated sampling, medians, and MAD
• check in reproducible performance, spec-coverage, and safety/type evidence
• add cross-platform CI evidence summaries and bounded benchmark smoke checks

Verification

• cargo fmt --check
• cargo clippy --all-targets -- -D warnings
• cargo test --release
• tools/phase0_audit.py check
• benches/run.sh fib strings bigint --samples 3 --warmups 0 --max-vm-ms 5000

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.