paper: teacher at greedy — same-protocol shrink +1.60pp

[ronaldtse]

Summary

• teacher measured at greedy on the same harness: 1.25% PER (EM 95.16%) vs its beam-4 4.43% — the beam pathology inflated the teacher too; same-protocol client-tier shrink cost is +1.60pp, not +7.63pp
• frontier figure, RESULTS table, metadata, metrics chain, and paper text all updated (PRs paper: bootstrap CI for the decode comparison #47/metrics: tha ref back to main #48 landed the chain)

Test plan

• CI green