Release SkipHow 4.5.1 with precise context routing

[mzored]

Summary

• remove the dated host-mechanics snapshot from shipped delegation guidance while retaining the portable read-only fallback
• stop fast-fixes from loading integration guidance before delivery
• add a narrow runtime-portability gate and release evidence for the measured context reduction

Verification

• focused package, workflow, and eval tests: 226 passed
• independent read-only review of candidate 4250c7a: no qualifying findings
• full deterministic gate: PASS
• git diff --check: PASS
• Codex schema validation: PASS
• Claude schema validation: PASS
• Claude isolated install and uninstall: PASS on the exact 22-file payload
• Codex isolated install: UNVERIFIED because managed source policy refused the local marketplace before installation
• paid behavioral sessions: not run; behavior remains UNVERIFIED

The two pre-existing untracked audit files are not part of this branch.