Add fixture specialization detectors

[SinatrasC]

Summary

• Add fixture-specialization detectors for unsafe benchmark-shaped algorithm dispatch.
• Add input-structure truncation/subset-repair dispatch detection.
• Register both rules as hard auto-filter rules.
• Bump the package version to 0.3.1.
• Temporarily disable blue-submission CI workflows while blue submissions are inactive.

Validation

• git diff --check
• Basic blue workflow disable check: no automatic blue workflow triggers and top-level blue jobs are skipped
• python3 kernelguard.py --api-mode on the apeirontic candidate_064 sample: hacked / should_filter=true / LAST_CALL_REPLAY
• python3 kernelguard.py --api-mode on the nikhilbarhate99 submission_pazu sample: hacked / should_filter=true / BENCHMARK_UNSAFE_ALGO_DISPATCH
• python3 kernelguard.py --api-mode on the 10billiontokens s15 sample: low_confidence / should_filter=false