docs(projects): link supporting reviewer paths

[stacknil]

Summary

• add an ordered reviewer path for the extended precipitation diagnostics lab
• route the root README and root reviewer brief to real supporting-project reviewer paths
• extend the reviewer route contract to validate six reviewer documents and four reviewer paths
• ignore generated editable-install egg-info metadata at the repository root

Validation

• python scripts\\validate-reviewer-routes.py
• git diff --cached --check
• python -m unittest discover -s tests from projects/precipitation-anomaly-diagnostics-lab
• extended lab CLI help smoke tests for precipitation anomalies, EOF, composite circulation, index correlations, lag diagnostics, MCA, regression, and trend diagnostics
• python examples\\generate_synthetic_demo_assets.py from projects/precipitation-anomaly-diagnostics-lab; no tracked artifact diff
• changed-file privacy/sensitive-pattern scan: no matches for local paths, institution identifiers, credentials, or secret-like terms

Notes

No runtime behavior changes; this tightens reviewer navigation and the executable route contract.