Add hover labels to plotly event study, complete __all__ exports

- Attach customdata + hovertemplate to plotly event study point traces so
  hover shows real period labels instead of ordinal positions
- Add plot_bacon, plot_power_curve, plot_pretrends_power to __all__
- Expand export regression test to cover all 11 plotting helpers

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

Author: igerber

diff_diff/__init__.py

@@ -255,10 +255,13 @@
     "EDiDBootstrapResults",
     "EDiD",
     # Visualization
+    "plot_bacon",
     "plot_event_study",
     "plot_group_effects",
     "plot_sensitivity",
     "plot_honest_event_study",
+    "plot_power_curve",
+    "plot_pretrends_power",
     "plot_synth_weights",
     "plot_staircase",
     "plot_dose_response",

diff_diff/visualization/_event_study.py

@@ -492,11 +492,17 @@ def _render_event_study_plotly(
             )
         )
 
-    # Point estimates — separate reference vs non-reference
+    # Point estimates — separate reference vs non-reference.
+    # Attach original period labels via customdata + hovertemplate so hover
+    # shows real periods instead of ordinal positions.
     non_ref_x = [period_to_x[p] for p, r in zip(periods, is_ref) if not r]
     non_ref_e = [e for e, r in zip(effects, is_ref) if not r]
+    non_ref_labels = [str(p) for p, r in zip(periods, is_ref) if not r]
     ref_x = [period_to_x[p] for p, r in zip(periods, is_ref) if r]
     ref_e = [e for e, r in zip(effects, is_ref) if r]
+    ref_labels = [str(p) for p, r in zip(periods, is_ref) if r]
+
+    hover_tpl = "Period: %{customdata}<br>Effect: %{y:.4f}<extra></extra>"
 
     if non_ref_x:
         fig.add_trace(
@@ -506,6 +512,8 @@ def _render_event_study_plotly(
                 mode="markers",
                 marker=dict(color=color, size=10),
                 name="Effect",
+                customdata=non_ref_labels,
+                hovertemplate=hover_tpl,
             )
         )
 
@@ -521,6 +529,8 @@ def _render_event_study_plotly(
                     line=dict(color=color, width=2),
                 ),
                 name="Reference",
+                customdata=ref_labels,
+                hovertemplate=hover_tpl,
             )
         )
 

tests/test_visualization_plotly.py

@@ -283,10 +283,17 @@ def test_cmap_not_swapped(self, cs_results):
 class TestTopLevelExports:
     """Regression: new plot functions must be in diff_diff.__all__."""
 
-    def test_new_plots_in_all(self):
+    def test_all_plots_in_all(self):
         import diff_diff
 
         for name in [
+            "plot_bacon",
+            "plot_event_study",
+            "plot_group_effects",
+            "plot_sensitivity",
+            "plot_honest_event_study",
+            "plot_power_curve",
+            "plot_pretrends_power",
             "plot_synth_weights",
             "plot_staircase",
             "plot_dose_response",