Clean up completed items from TODO.md and ROADMAP.md

[igerber]

Summary

• Remove completed/strikethrough sections and rows from TODO.md (NaN handling, safe_inference migration, 10 fixed tech debt rows, Fix Plan subsection, 5 completed module splits)
• Update ROADMAP.md: version to v2.4.1, remove shipped Two-Stage DiD section, bump Near-Term milestone to v2.5
• Fix factual error in CHANGELOG.md (actual change was @ → np.dot(), not the reverse)

Methodology references (required if estimator / math changes)

• N/A - documentation-only changes, no estimator or math code modified

Validation

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

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

• Docs-only updates in CHANGELOG.md, ROADMAP.md, and TODO.md; no estimator or inference code touched.
• Methodology registry docs/methodology/REGISTRY.md and code docstrings are unaffected by this diff; no assumptions/variance changes to validate.
• Edge-case checklist not applicable because there are no new code paths or parameters.
• Tests not run (docs-only changes).

Methodology

• Severity: P3 (Info). Impact: Documentation-only changes; no estimator, math, weighting, variance/SE, or default behavior changes to cross-check against docs/methodology/REGISTRY.md or docstrings. Fix: None.

Code Quality

• Severity: P3 (Info). Impact: No code changes in scope. Fix: None.

Performance

• Severity: P3 (Info). Impact: No performance-impacting code changes in scope. Fix: None.

Maintainability

• Severity: P3 (Info). Impact: Doc cleanup only; no maintainability risk introduced in code. Fix: None.

Tech Debt

• Severity: P3 (Info). Impact: Completed items removed from TODO; no new tech debt introduced. Fix: None.

Security

• Severity: P3 (Info). Impact: No code/config changes; no new secret exposure risk. Fix: None.

Documentation/Tests

• Severity: P3 (Info). Impact: Documentation updates only; tests not run. Fix: None.