receipt gate: '0 -> full gate' wording overstates (receipt_ok_arg.sh:5, ci_receipt_gate.sh:14) #5805

Follow-up from the #5798 review @64c2971d8e (receipt quorum/claude-lane-5798-64c2971d8e). The comments at scripts receipt_ok_arg.sh:5 and ci_receipt_gate.sh:14 say ok=0 falls back to the full gate. Reword them to match what the tier selection actually runs. Comment-only. Also track: hosted rustc -vV parity with the batcher is unproven (fails closed); close it on the first real batcher-signed run.