Correct the shell policy reduction gate

[Aaronontheweb]

Summary

• count the complete changed production footprint
• treat every added production file as zero baseline lines
• record the failed preliminary reduction audit
• keep the original seven-file threshold as a second gate

Evidence

• original files: 5,136 to 4,589 lines
• complete footprint: 6,680 to 8,164 lines
• complete control flow: 452 to 504 lines
• actor coverage: 3,411 passed and one expected skip
• security coverage: 927 passed
• strict OpenSpec validation passed
• git diff --check passed

This PR changes planning artifacts only. It does not change runtime behavior.