Rebuild public proof observatory and fix artifact streaming

[JROChub]

Summary

• rebuild mfenx.com as a full-screen proof instrument with proof-reactive WebGL, world observatory, responsive telemetry, and technical evaluation intake
• fix Megaround and Committed browser verification by buffering against canonical uncompressed artifact sizes instead of gzip Content-Length
• add local PHSP/PHSM/PHCP verification, regression coverage, documentation, attribution, and release notes

Verification

• cargo fmt --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test --all-targets --locked
• cargo test --all-targets --features net --locked
• all release examples and independent Python artifact verification
• sparse mutation/conformance and soundness-budget tests
• browser checks for all four modes, local files, WebGL fallback, desktop/tablet/mobile layouts, and canvas output
• node scripts/test_observatory_stream.mjs