Add public read-only methodology surface

[FransDevelopment]

Summary

• expand PR Add public read-only methodology surface #28 from calibration-ledger-lite into the broader public read-only LOVS methodology surface described in Earth
• keep the public calibration ledger with 15 pre-registered accountability commitments and commitment hashes
• add calibration status, precommitment targets, blindspots, latency observatory, nowcast status, and a read-only interface contract
• update source traceability with public data-as-of fields, release provenance, docs, and tests

Added public artifacts

• data/public_calibration_ledger.csv
• data/public_calibration_status.json
• data/public_precommitment_targets.csv
• data/public_blindspots.json
• data/public_latency_observatory.csv
• data/public_nowcast_status.json
• READONLY_INTERFACE_PUBLIC.md
• CALIBRATION_LEDGER_PUBLIC.md

Boundary

This still does not expose source-ingest automation, mutable resolver tools, private-data adapters, model parameters, probability intervals, scoring implementation, or internal calibration code.

Validation

• python3 -m lovs.public_exports --check
• python3 -m unittest discover -s tests
• python3 -m lovs.public_repo_hygiene
• python3 -m compileall -q lovs tests
• git diff --check
• sensitive-term scan over expanded public data artifacts
• engineering gates: plan_complete, glossary_present, assumptions_verified, diff_matches_plan, red_team_complete

Review focus

Please review whether this is now the right public-good disclosure: enough for MOH/CDC/WHO and public-repo users to inspect the methodology discipline, without making the repo a cloneable LOVS engine.