[ZhenHaoFu810]

Summary

• Sync the July 2026 v1.2.0+ correctness-hardening candidate to the public repository.
• Refresh README, Chinese README, changelog, release status, known issues, and release-candidate checklist.
• Publish the manifest-selected code/test/docs hardening changes without internal audit workspaces or golden test artifacts.

Validation

Main repository:

• python -m compileall -q src/stataflow
• python -c "import stataflow; print(stataflow.__version__); print(stataflow.OLS.__name__)"
• pytest tests/ -q --ignore=tests/golden/ --ignore=tests/audit_v1_3: 405 passed, 76 warnings

Public mirror:

• pytest tests/ -q --ignore=tests/golden/ --ignore=tests/audit_v1_3: 397 passed, 76 warnings
• python -m compileall -q src/stataflow tests
• python -c "import stataflow; print(stataflow.__version__)"
• python examples/demo_regress.py
• python examples/demo_reghdfe.py
• python examples/demo_ppmlhdfe.py
• python examples/demo_ivregress_2sls.py
• python -m pip wheel . --no-deps -w dist_tmp

Notes

Package version remains 1.1.0. This PR is a correctness-hardening release-candidate sync for the v1.2.0+ line.

[Copilot]

Pull request overview

Publishes a July 2026 v1.2.0+ correctness-hardening release-candidate sync to the public repository, pairing targeted estimator/schema hardening with a broad documentation and release-status refresh while keeping the package version at 1.1.0.

Changes:

• Extends ResultSchema coefficient serialization to preserve Stata factor-variable base/omitted metadata and adds regression/RD/FE/IV/PPML correctness alignment tweaks.
• Updates DID-imputation semantics/tests around “never-treated” encoding and documents wrapper-vs-native option boundaries (notably window).
• Refreshes README(s), changelog, open-source status, known issues, and release-candidate checklist for the public sync.

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tests/test_result_schema.py	Adds JSON round-trip coverage for factor base/omitted flags.
tests/test_rdrobust.py	Adds warning assertion for low effective sample in RD.
tests/test_compat_stata_linear.py	Adds FE clustered df_model and residuals contract tests.
tests/test_compat_stata_iv.py	Adds near-collinearity regression drop consistency test for IV.
tests/test_compat_stata_hdfe.py	Adds near-collinearity and df_a/df_resid reproduction tests for HDFE/PPMLHDFE.
tests/test_compat_stata_glm.py	Adds near-collinearity consistency test for logit.
tests/test_compat_stata_did.py	Switches DID test data to missing-as-never-treated and refines wrapper/native option expectations.
src/stataflow/results/result.py	Serializes is_base/is_omitted for coefficient rows.
src/stataflow/estimators/rdrobust.py	Emits a diagnostics warning for low effective observations.
src/stataflow/estimators/ppmlhdfe.py	Sets clustered df_resid to missing (NaN) to match Stata semantics.
src/stataflow/estimators/iv.py	Adjusts weak-ID constant counting and FE small-sample scaling in robust/OLS VCE paths.
src/stataflow/estimators/fe.py	Aligns clustered df_model storage and clarifies residual prediction contract (y - xb).
src/stataflow/estimators/eventstudyinteract.py	Tweaks cluster small-sample adjustment to include the implicit constant.
src/stataflow/estimators/did_imputation.py	Treats any finite first_treat as an ever-treated cohort (missing-only never-treated).
src/stataflow/compat/stata/did.py	Explicitly rejects window in the Stata-compatible did_imputation wrapper.
src/stataflow/init.py	Clarifies package-level docstring positioning and wording.
README.zh-CN.md	Refreshes positioning, feature summary, examples, and validation notes.
README.md	Refreshes positioning, feature summary, examples, and validation notes.
docs/research/did_imputation.md	Adds research archive describing target ado behavior and estimator contract.
docs/research/did_imputation-options.md	Adds options-focused research archive, including window() boundary.
docs/release/release-candidate-checklist.md	Updates RC checklist for July 2026 sync and validation gates.
docs/release/open-source-status.md	Updates open-source status model and July 2026 sync summary.
docs/release/known-issues.md	Records the July 2026 hardening update and re-frames known issues.
docs/command-support-matrix/did-imputation.md	Adds did_imputation support matrix including wrapper/native boundaries.
docs/architecture/result-schema.md	Documents ResultSchema contract including factor-row metadata fields.
CHANGELOG.md	Adds v1.2.0+ correctness-hardening sync entry (version remains 1.1.0).

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