Update TripleDifference summary table to reflect completed review

[igerber]

Summary

• Update TripleDifference row in the Review Status Summary table to show triplediff::ddd() reference, Complete status, and review date
• PR Rewrite TripleDifference to match R's triplediff::ddd() #169 updated the detailed section but missed the summary table at the top of METHODOLOGY_REVIEW.md

Methodology references (required if estimator / math changes)

• N/A - documentation-only change

Validation

• No test changes
• Visual inspection: summary table now matches detailed section

Security / privacy

• Confirm no secrets/PII in this PR: Yes

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Generated with Claude Code

[github-actions]

Overall assessment: ✅ Looks good

Executive summary

• Summary table row for TripleDifference now matches the detailed review section (R reference, status, and date). METHODOLOGY_REVIEW.md:L21-L33, METHODOLOGY_REVIEW.md:L425-L433
• No estimator, math, variance/SE, or assumption changes; no methodology registry cross-check required for this PR.
• Documentation-only change; no code paths or tests impacted.

Methodology

• P3 | Impact: Documentation-only update; summary row is consistent with the detailed TripleDifference review section. | Fix: None. METHODOLOGY_REVIEW.md:L21-L33, METHODOLOGY_REVIEW.md:L425-L433

Code Quality

• P3 | Impact: No code changes; no quality risks introduced. | Fix: None.

Performance

• P3 | Impact: No runtime changes. | Fix: None.

Maintainability

• P3 | Impact: Improves documentation consistency; no maintenance risks introduced. | Fix: None.

Tech Debt

• P3 | Impact: No new debt introduced. | Fix: None.

Security

• P3 | Impact: No code or dependency changes; no secrets added. | Fix: None.

Documentation/Tests

• P3 | Impact: Documentation-only change; tests not required. | Fix: None.