Add methodology workflow checklist to CLAUDE.md

[igerber]

Summary

• Add docs/methodology/REGISTRY.md to documentation section as first-class reference
• Add new "Implementing Methodology-Critical Code" development checklist
• Strengthen "Adding Warning/Error/Fallback Handling" checklist with Registry consultation and np.errstate guidance
• Update "For Bug Fixes or Minor Enhancements" to require methodology registry updates

Methodology references (required if estimator / math changes)

• Method name(s): N/A - no estimator/math changes
• Paper / source link(s): N/A
• Any intentional deviations from the source (and why): N/A

Validation

• Tests added/updated: No test changes (documentation-only PR)
• Backtest / simulation / notebook evidence (if applicable): N/A

Security / privacy

• Confirm no secrets/PII in this PR: Yes

Context

PR #95 required multiple review rounds due to:

1. Non-finite handling wasn't documented as intentional deviation from reference implementations
2. Tests captured warnings but didn't assert on methodology-aligned behavior
3. Edge case handling wasn't clearly tied to documented methodology

These CLAUDE.md changes would have prevented those issues by:

• Requiring consultation of docs/methodology/REGISTRY.md before implementing methodology changes
• Mandating documentation when deviating from R/Stata reference behavior
• Requiring tests that assert warnings are raised AND the warned-about behavior occurred

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Generated with Claude Code

[github-actions]

Overall assessment: ✅ Looks good

Executive summary

• Documentation-only change; no estimator/methodology code touched.
• Adds clear checklist to enforce consultation and updates of docs/methodology/REGISTRY.md.
• No tests or code changes required for this PR.

Methodology

• No findings. Changes are documentation-only (CLAUDE.md).

Code Quality

• No findings.

Performance

• No findings.

Maintainability

• No findings.

Tech Debt

• No findings.

Security

• No findings.

Documentation/Tests

• No findings. Documentation update is consistent and scoped (CLAUDE.md).