Bump version to 3.13.0

[igerber]

Summary

• Bump version 3.12.0 -> 3.13.0 in diff_diff/__init__.py, pyproject.toml, rust/Cargo.toml, diff_diff/guides/llms-full.txt, and CITATION.cff (date-released: 2026-10-17).
• Compile the six pending changelog.d/ fragments into CHANGELOG.md [3.13.0] - 2026-10-17 and add the comparison link; fragments deleted by the compiler.
  • Added: TWFE weight diagnostics (feat: TWFE weight diagnostics (twfeweights R port, re-scoped from #753) #812)
  • Behavioral: DMLDiD cross-fit learner isolation fails closed (fix(dml): fail closed when cross-fit learners cannot be isolated #816)
  • Fixed: deprecation-sentinel copy identity; CS bootstrap event-study vcov (fix(staggered): carry the bootstrap event-study covariance instead of clearing it #839); SC in-space placebo donor pool (fix(synthetic_control): put the treated unit in every in-space placebo's donor pool #841); SC exact simplex donor weights (fix(synthetic_control): solve the donor weights exactly by non-negative least squares #842)
• Extend _NEXT_RELEASE in tests/test_naming_guard.py with (3, 13): "4.0" so the version-keyed lifecycle gate re-arms (same step as the 3.12.0 bump, Bump version to 3.12.0 #832).

Methodology references (required if estimator / math changes)

• Method name(s): N/A - no methodology changes (version metadata and changelog only)
• Paper / source link(s): N/A
• Any intentional deviations from the source (and why): None

Validation

• Tests added/updated: tests/test_naming_guard.py (_NEXT_RELEASE map entry)
• Ran locally: tests/test_changelog_fragments.py, tests/test_tracking_files.py, tests/test_docs_ia.py (183 passed); tests/test_naming_guard.py lifecycle-gate test passes with the new entry.
• Backtest / simulation / notebook evidence (if applicable): N/A

Security / privacy

• Confirm no secrets/PII in this PR: Yes

Changelog

• changelog.d/ fragment added (or N/A - no user-visible change): N/A - this PR compiles the fragments into the release section.

[github-actions]

Overall Assessment

✅ Looks good — no unmitigated P0/P1 findings.

Executive Summary

• Release-only changes; no estimator, weighting, inference, or methodology logic changed.
• Version metadata is consistently updated to 3.13.0.
• Changelog fragments were correctly compiled outside Unreleased.
• Changelog validation and git diff --check pass.
• No security, performance, or technical-debt concerns found.

Methodology

No findings. The affected files do not modify causal methods or assumptions. Relevant Registry entries remain unchanged.

Code Quality

No findings. The lifecycle mapping update in tests/test_naming_guard.py:L111-L116 is consistent with the existing release-horizon contract.

Performance

No findings. No runtime code paths changed.

Maintainability

No findings. Version values agree across diff_diff/__init__.py:L385, pyproject.toml:L7, rust/Cargo.toml:L3, and CITATION.cff:L9-L10.

Tech Debt

No findings.

Security

No findings. The diff contains no secrets or security-sensitive changes.

Documentation/Tests

No findings. CHANGELOG.md:L10-L183 contains a proper versioned release section, while Unreleased remains pointer-only. The fragment checker passes.

Full targeted pytest execution was unavailable because pytest is not installed in the review environment.