Bump version to 2.3.0

[igerber]

Summary

• Bump version from 2.2.1 to 2.3.0 across all version files
• Add CHANGELOG entry for v2.3.0 covering:
  • Borusyak-Jaravel-Spiess (2024) Imputation DiD estimator
  • TWFE within-transformation bug fix and methodology review
  • New skills: /paper-review, /read-feedback-revise, review-plan flags
  • MultiPeriodDiD vs R (fixest) benchmark
  • Test suite runtime improvements

Methodology references (required if estimator / math changes)

• N/A - version bump and changelog only (no methodology code changes)

Validation

• No test changes (version bump only)
• Version updated in: diff_diff/__init__.py, pyproject.toml, rust/Cargo.toml
• CHANGELOG comparison link added for [2.3.0]

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

• Version bump to 2.3.0 across Python/Rust metadata plus a new changelog entry; no estimator or inference code changes in this diff.
• Methodology registry cross-check for the ImputationDiD release notes shows no conflicts with documented assumptions/variance items.
• Edge-case checklist not triggered because no new code paths were introduced.
• No tests updated in this PR.

Methodology

• P3 (Info) — No estimator/math/SE/default-behavior code changes in this diff; the ImputationDiD changelog bullets align with the Methodology Registry items (Theorem 3 variance, pre-trend test, absorbing treatment, long-run horizon warning). Impact: None. Fix: None. (CHANGELOG.md:L10-L21, docs/methodology/REGISTRY.md:L451-L551)

Code Quality

• P3 (Info) — No runtime logic changes; only version strings updated. Impact: None. Fix: None. (diff_diff/init.py:L145, pyproject.toml:L7, rust/Cargo.toml:L3)

Performance

• P3 (Info) — No performance-affecting code changes in this diff. Impact: None. Fix: None.

Maintainability

• P3 (Info) — Release metadata and changelog updates only; no maintainability impacts. Impact: None. Fix: None.

Tech Debt

• P3 (Info) — No new tech debt introduced by this version/changelog update. Impact: None. Fix: None.

Security

• P3 (Info) — No code or dependency changes; nothing security-sensitive in scope. Impact: None. Fix: None.

Documentation/Tests

• P3 (Info) — Changelog updated for 2.3.0; no test changes in this PR. Impact: None. Fix: None. (CHANGELOG.md:L10-L36)