docs(v4): item 9 of the 4.0 cut - diagnostic-family roster reorganization (M-090 done)

.claude/commands/docs-check.md

@@ -52,7 +52,7 @@ The following estimators/features MUST have documentation:
 | WooldridgeDiD | "WooldridgeDiD" | "WooldridgeDiD" | wooldridge_etwfe.rst | "Multi-Period and Staggered" |
 | TROP | "TROP" | "TROP" | trop.rst | "Triply Robust Panel" |
 | HonestDiD | n/a (in `## Diagnostics`) | n/a (in `## Diagnostics`) | honest_did.rst | "Honest DiD" |
-| BaconDecomposition | "BaconDecomposition" | "BaconDecomposition" | bacon.rst | "Multi-Period and Staggered" |
+| BaconDecomposition | n/a (in `## Diagnostics and Sensitivity Analysis`) | n/a (in `## Diagnostics & Sensitivity`) | bacon.rst | "Multi-Period and Staggered" |
 
 ### Supporting Features (require llms.txt mention + API docs; README mention only if landing-page-relevant)
 
@@ -117,11 +117,11 @@ Determine which checks to run based on `$ARGUMENTS`.
 For each estimator/diagnostic in the table above:
 
 1. Read `diff_diff/guides/llms.txt` and verify the name appears under the right section:
-   - **Estimators** (e.g. CallawaySantAnna, SunAbraham, TROP, BaconDecomposition): under `## Estimators`
-   - **Diagnostics-class** (HonestDiD, and any future diagnostic-only entries): under `## Diagnostics and Sensitivity Analysis`
+   - **Estimators** (e.g. CallawaySantAnna, SunAbraham, TROP): under `## Estimators`
+   - **Diagnostics-class** (HonestDiD, BaconDecomposition, RDPlot, RDDensityTest, and any future diagnostic-only entries): under `## Diagnostics and Sensitivity Analysis`
 2. Read `README.md` and verify the name appears in the matching flat catalog:
    - **Estimators**: in the `## Estimators` section
-   - **Diagnostics-class** (HonestDiD): in the `## Diagnostics & Sensitivity` section
+   - **Diagnostics-class** (HonestDiD, BaconDecomposition, RDPlot, RDDensityTest): in the `## Diagnostics & Sensitivity` section
 3. Report missing entries
 
 ```bash

.github/workflows/docs-tests.yml

@@ -11,6 +11,11 @@ on:
       - 'tests/test_docs_ia.py'
       - 'tests/test_v4_matrix.py'
       - 'tests/test_naming_guard.py'
+      # Diagnostic-family roster guard (M-090): README-only diffs otherwise
+      # run no lane that executes it - rust-test.yml fires on tests/** and
+      # diff_diff/** only.
+      - 'tests/test_v4_diagnostic_family_docs.py'
+      - 'README.md'
       # Changelog-fragment guard: the fragment store, the compiler, and
       # CHANGELOG.md itself trigger here (their ONLY CI lane - rust-test.yml
       # deliberately does not fire on fragment-only diffs).
@@ -48,6 +53,11 @@ on:
       - 'tests/test_docs_ia.py'
       - 'tests/test_v4_matrix.py'
       - 'tests/test_naming_guard.py'
+      # Diagnostic-family roster guard (M-090): README-only diffs otherwise
+      # run no lane that executes it - rust-test.yml fires on tests/** and
+      # diff_diff/** only.
+      - 'tests/test_v4_diagnostic_family_docs.py'
+      - 'README.md'
       - 'tests/test_changelog_fragments.py'
       - 'changelog.d/**'
       - 'CHANGELOG.md'
@@ -129,6 +139,13 @@ jobs:
         # the main test matrix does not trigger on docs-only diffs.
         run: PYTHONPATH=. DIFF_DIFF_BACKEND=python pytest tests/test_v4_matrix.py -v
 
+      - name: Run diagnostic-family roster guard
+        # Pins the M-090 estimators/diagnostics split on README, llms.txt,
+        # llms-full.txt, docs/index.rst, docs/api/index.rst and the REGISTRY
+        # archive framing; docs-only and README-only diffs do not trigger the
+        # main matrix.
+        run: PYTHONPATH=. DIFF_DIFF_BACKEND=python pytest tests/test_v4_diagnostic_family_docs.py -v
+
       - name: Run naming-completeness guard
         # The section-8/section-9 naming guard (spec in the module docstring):
         # public-surface vocabulary sweep, phase-table agreement in both

README.md

@@ -121,7 +121,6 @@ Full guide: `diff_diff.get_llm_guide("practitioner")`.
 - [LWDiD](https://diff-diff.readthedocs.io/en/stable/api/lwdid.html) - Lee & Wooldridge (2025, 2026) rolling-transformation DiD: unit-specific demean/detrend converts panel to cross-section, staggered adoption, `estimation_method` in `reg`/`ipw`/`dr`/`psm` (the papers' RA/IPW/IPWRA plus propensity-score matching), exact small-N inference on the classical collapsed regression
 - [DMLDiD](https://diff-diff.readthedocs.io/en/stable/api/dml_did.html) - Chang (2020) double/debiased machine learning DiD: staggered ATT(g,t) with cross-fitted ML nuisance learners (DML2) and Neyman-orthogonal scores, for flexible/high-dimensional covariate adjustment under conditional parallel trends; panel or declared repeated cross sections (`panel=False`); survey/cluster support on both lanes (bad-control lane: panel only, `cluster=` only); Caetano, Callaway, Payne & Sant'Anna (2026) bad-control score via `fit(bad_control=, bad_control_covariates=)`
 - [DurationDiD](https://diff-diff.readthedocs.io/en/stable/api/duration_did.html) - Deaner & Ku (2026) causal duration DiD for a binary absorbing outcome (spell ended) in a two-group common-timing design: restricts the groups' untreated hazards (`method="cd"` additive gap or `method="ph"` ratio) instead of outcome levels, imputes the treated counterfactual survival, reports the per-date absorption ATT with whole-individual bootstrap pointwise and simultaneous bands plus a fixed-anchor pre-treatment specification test
-- [BaconDecomposition](https://diff-diff.readthedocs.io/en/stable/api/bacon.html) - Goodman-Bacon (2021) decomposition for diagnosing TWFE bias in staggered settings
 
 ## Diagnostics & Sensitivity
 
@@ -131,6 +130,7 @@ Full guide: `diff_diff.get_llm_guide("practitioner")`.
 - [Parallel Trends Testing](https://diff-diff.readthedocs.io/en/stable/api/diagnostics.html) - simple and Wasserstein-robust parallel trends tests, equivalence testing (TOST)
 - [Placebo Tests](https://diff-diff.readthedocs.io/en/stable/api/diagnostics.html) - placebo timing, group, permutation, leave-one-out
 - [TWFE Weight Diagnostics](https://diff-diff.readthedocs.io/en/stable/api/twfe_weights.html) - Baker et al. (2025) implicit weights a TWFE regression places on each ATT(g,t), against the ATT^O / ATT^simple targets, with the pre-period contribution. Ports Callaway's `twfeweights` (MIT)
+- [Bacon Decomposition](https://diff-diff.readthedocs.io/en/stable/api/bacon.html) - Goodman-Bacon (2021) decomposition of the TWFE estimate into its 2x2 comparisons and weights, for diagnosing TWFE bias in staggered settings (`BaconDecomposition`, alias `Bacon`)
 - [Honest DiD](https://diff-diff.readthedocs.io/en/stable/api/honest_did.html) - Rambachan & Roth (2023) sensitivity analysis: robust CI under PT violations, breakdown values
 - [Pre-Trends Power Analysis](https://diff-diff.readthedocs.io/en/stable/api/pretrends.html) - Roth (2022) minimum detectable violation and power curves
 - [Power Analysis](https://diff-diff.readthedocs.io/en/stable/api/power.html) - analytical and simulation-based MDE, sample size, power curves for study design

changelog.d/20261101-v4-pr9-m090-docs-reorg.md

@@ -0,0 +1,9 @@
+### Documentation
+
+- `BaconDecomposition` is re-homed into the diagnostics family ([M-090], item 9 of the 4.0 cut): it leaves the estimator catalogues - README `## Estimators`, `llms.txt` `## Estimators`, the `llms-full.txt` Estimators section and its alias line, the API-reference Estimators autosummary and module toctree, and the docs homepage Supported Estimators table - for their Diagnostics groupings. `RDPlot` moves from the API-reference Visualization autosummary into Diagnostics; `RDPlot`, `RDDensityTest` and the TWFE weight diagnostics leave the `llms-full.txt` Estimators section. Docs-only: the import path, the `Bacon` alias, the results class and every number are unchanged.
+- The docs homepage gains a "Diagnostics & Sensitivity" table (BaconDecomposition, RDPlot, RDDensityTest, HonestDiD, PreTrendsPower, PowerAnalysis, DiagnosticReport, the parallel-trends / placebo / TWFE-weight functions and the HAD pretest workflow) next to the estimator table; the API-reference Estimators and Diagnostics intros describe the split.
+- `docs/methodology/REGISTRY.md` archive framing for the classes removed at 4.0: the MultiPeriodDiD and StaggeredTripleDifference sections and the QDiD class-spelling subsection open with an archive Note, the table of contents marks them *(archived)* and states the archived-sections convention, the cross-reference tables name `ChangesInChanges(method="qdid")` instead of a standalone `QDiD` estimator, and the "20-estimator count" wording is gone. The migration guide gains the [M-090] bullet.
+
+### Internal
+
+- Ledger row M-090 flips to `done` with `tests/test_v4_diagnostic_family_docs.py` as its `test_ref`; the test pins the estimators/diagnostics split on README, `llms.txt`, `llms-full.txt`, `docs/index.rst`, `docs/api/index.rst` and the REGISTRY archive framing, and runs in the docs-tests workflow (README-only diffs now trigger that lane). `docs/doc-deps.yaml` points the diagnostic modules at the new homepage table; the `/docs-check` classification table files Bacon as a diagnostics-class entry.