Strengthen proof public boundary README

[midiakiasat]

Summary

Strengthen the proof public README so its proof-publication role is explicit, bounded, and non-overlapping.

Before

• thin surface
• weaker public boundary articulation than the strengthened sovereign surfaces
• insufficient explicit non-overlap at the README perimeter

After

• exact proof opening definition
• normalized ## Status
• normalized ## Boundary
• normalized ## What it does
• normalized ## What it does not do
• normalized ## Adjacent sovereign surfaces
• normalized ## Public host ownership
• normalized ## Public surface
• normalized ## Package / host / repo truth
• normalized ## Proof meaning in-system
• normalized ## Not this
• preserved required live host identity lines for https://proof.verifrax.net

Verification

• # proof
• ## Status
• ## Boundary
• ## What it does
• ## What it does not do
• ## Adjacent sovereign surfaces
• ## Public surface
• ## Package / host / repo truth
• ## Proof meaning in-system
• ## Not this
• https://proof.verifrax.net
• Apache License Version 2.0