feat(rd): comprehensive RDD mega-upgrade — 6 new modules + major enhancements

New modules (6 files, ~6000 lines):
- bandwidth.py: Full bandwidth selection suite (8 methods: MSE/CER × common/separate/comb1/comb2)
  with fuzzy-specific and covariate-adjusted support (Calonico-Cattaneo-Farrell 2020)
- locrand.py: Local randomization inference framework (rdrandinf, rdwinselect, rdsensitivity,
  rdrbounds) with Fisher exact tests and Rosenbaum bounds (Cattaneo-Titiunik-VB 2016)
- hte.py: Heterogeneous treatment effects via fully interacted local linear model (rdhte,
  rdbwhte, rdhte_lincom) with Wald heterogeneity test (Calonico et al. 2025)
- rd2d.py: Boundary discontinuity / 2D RD designs with distance-based and location-based
  approaches, bivariate local polynomial (Cattaneo-Titiunik-Yu 2025)
- extrapolate.py: External validity — Angrist-Rokkanen extrapolation (OLS/IPW/AIPW),
  multi-cutoff extrapolation, external validity diagnostics
- rdml.py: ML+RD methods — Causal Forest, Gradient Boosting, LASSO-assisted RD,
  unified CATE summary with variable importance

Major upgrades to existing modules:
- rdrobust.py: Covariate-adjusted local polynomial estimation (covariates in design matrix
  per Calonico et al. 2019), 8 bandwidth selectors (CER-optimal added), weights support,
  IMSE-optimal binning for rdplot, weighted global polynomial fits, pointwise CI bands
- diagnostics.py: Enhanced rdsummary with full=True mode (honest CI, power analysis,
  placebo tests, bandwidth comparison), multi-panel diagnostic dashboard plot
- __init__.py: All 30+ new public functions exported at sp.xxx level

57 tests pass (25 existing + 32 new). Total RD module: 10,298 lines across 14 files.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: brycewang-stanford

src/statspai/__init__.py

@@ -43,7 +43,15 @@
     aggte, cs_report, CSReport, ggdid,
     bjs_pretrend_joint,
 )
-from .rd import rdrobust, rdplot, rdplotdensity, rdbwsensitivity, rdbalance, rdplacebo, rdsummary, rkd, rd_honest, rdit, rdpower, rdsampsi
+from .rd import (
+    rdrobust, rdplot, rdplotdensity, rdbwselect,
+    rdbwsensitivity, rdbalance, rdplacebo, rdsummary,
+    rkd, rd_honest, rdit, rdpower, rdsampsi,
+    rdrandinf, rdwinselect, rdsensitivity, rdrbounds,
+    rdhte, rdbwhte, rdhte_lincom,
+    rd_forest, rd_boost, rd_lasso, rd_cate_summary,
+    rd_extrapolate, rd_multi_extrapolate, rd_external_validity,
+)
 from .synth import (
     synth, SyntheticControl, synthplot, sdid, augsynth,
     demeaned_synth, robust_synth, gsynth, staggered_synth, conformal_synth,
@@ -164,6 +172,8 @@
 from .mendelian import mendelian_randomization, MRResult, mr_egger, mr_ivw, mr_median
 # Multi-cutoff / Geographic RD
 from .rd import rdmc, rdms, RDMultiResult
+# 2D Boundary RD (Cattaneo, Titiunik, Yu 2025)
+from .rd import rd2d, rd2d_bw, rd2d_plot
 # Continuous Treatment DID
 from .did import continuous_did
 
@@ -264,13 +274,28 @@
     "rdrobust",
     "rdplot",
     "rdplotdensity",
+    "rdbwselect",
     "rdbwsensitivity",
     "rdbalance",
     "rdplacebo",
     "rdsummary",
     "rkd",
     "rd_honest",
     "rdit",
+    "rdrandinf",
+    "rdwinselect",
+    "rdsensitivity",
+    "rdrbounds",
+    "rdhte",
+    "rdbwhte",
+    "rdhte_lincom",
+    "rd_forest",
+    "rd_boost",
+    "rd_lasso",
+    "rd_cate_summary",
+    "rd_extrapolate",
+    "rd_multi_extrapolate",
+    "rd_external_validity",
     # Synthetic Control
     "synth",
     "SyntheticControl",

src/statspai/rd/__init__.py

@@ -1,28 +1,63 @@
 """
 Regression Discontinuity (RD) module for StatsPAI.
 
-Provides:
-- Sharp, Fuzzy, and Kink RD estimation (CCT 2014)
-- Donut-hole RD for handling manipulation near the cutoff
-- MSE-optimal bandwidth selection
-- RD plots with binned scatter and polynomial fits
-- Bandwidth sensitivity analysis
-- Covariate balance tests at the cutoff
-- Placebo cutoff tests
+The most comprehensive Python RD toolkit, providing:
+
+**Core estimation:**
+- Sharp, Fuzzy, and Kink RD estimation with robust bias-corrected inference (CCT 2014)
+- Covariate-adjusted local polynomial estimation (Calonico et al. 2019)
+- Donut-hole RD for manipulation near cutoff
+- Regression Discontinuity in Time (Hausman-Rapson 2018)
+- Multi-cutoff and multi-score RD (Cattaneo et al. 2024)
+- Boundary discontinuity / 2D RD designs (Cattaneo-Titiunik-Yu 2025)
+
+**Bandwidth selection:**
+- MSE-optimal: mserd, msetwo, msecomb1, msecomb2
+- CER-optimal: cerrd, certwo, cercomb1, cercomb2 (Calonico-Cattaneo-Farrell 2020)
+- Fuzzy-specific and covariate-adjusted bandwidth selection
+
+**Inference:**
+- Honest confidence intervals (Armstrong-Kolesar 2018, 2020)
+- Local randomization inference with Fisher exact tests (Cattaneo-Titiunik-VB 2016)
+- Window selection and sensitivity analysis
+- Rosenbaum sensitivity bounds
+
+**Treatment effect heterogeneity:**
+- CATE estimation via fully interacted local linear (Calonico et al. 2025)
+- ML + RD: Causal Forest, Gradient Boosting, LASSO-assisted RD
+
+**External validity:**
+- Extrapolation away from cutoff (Angrist-Rokkanen 2015)
+- Multi-cutoff extrapolation (Cattaneo et al. 2024)
+- External validity diagnostics
+
+**Diagnostics & visualization:**
+- One-click diagnostic dashboard (rdsummary)
+- IMSE-optimal binned scatter with pointwise CI bands
+- Density manipulation testing (CJM 2020)
+- Bandwidth sensitivity, covariate balance, placebo cutoff tests
+- Power analysis and sample size calculations
 """
 
 from .rdrobust import rdrobust, rdplot, rdplotdensity
+from .bandwidth import rdbwselect
 from .diagnostics import rdbwsensitivity, rdbalance, rdplacebo, rdsummary
 from .rkd import rkd
 from .honest_ci import rd_honest
 from .rdit import rdit
 from .rdmulti import rdmc, rdms, RDMultiResult
 from .rdpower import rdpower, rdsampsi, RDPowerResult, RDSampSiResult
+from .locrand import rdrandinf, rdwinselect, rdsensitivity, rdrbounds
+from .hte import rdhte, rdbwhte, rdhte_lincom
+from .rd2d import rd2d, rd2d_bw, rd2d_plot
+from .rdml import rd_forest, rd_boost, rd_lasso, rd_cate_summary
+from .extrapolate import rd_extrapolate, rd_multi_extrapolate, rd_external_validity
 
 __all__ = [
     'rdrobust',
     'rdplot',
     'rdplotdensity',
+    'rdbwselect',
     'rdbwsensitivity',
     'rdbalance',
     'rdplacebo',
@@ -37,4 +72,21 @@
     'rdsampsi',
     'RDPowerResult',
     'RDSampSiResult',
+    'rdrandinf',
+    'rdwinselect',
+    'rdsensitivity',
+    'rdrbounds',
+    'rdhte',
+    'rdbwhte',
+    'rdhte_lincom',
+    'rd2d',
+    'rd2d_bw',
+    'rd2d_plot',
+    'rd_forest',
+    'rd_boost',
+    'rd_lasso',
+    'rd_cate_summary',
+    'rd_extrapolate',
+    'rd_multi_extrapolate',
+    'rd_external_validity',
 ]