[cschanhniem]

Implements C6 from NEXT_100_PR_MAP: bench-charge-length-matched control.

What

• charge_length_report.py: compute_charge_length_report() + format_charge_length_report() + ChargeLengthReport
• Tests CONJUNCTION of charge>=4 AND length [10,40] -- strongest single cheap AMP predictor
• combined_shortcut_likely=True when >=50% positives match BOTH AND ratio >=1.5x
• 63 tests; BASELINE 7087 to 7150

Why

Charge alone and length alone are weak shortcuts. Their conjunction is stronger. This report makes it visible and auditable.

Disconfirming pass

• Report is evidence only, does not block.
• No safety/release policy touched.