make multi in timespoken better

utils.py

@@ -538,17 +538,35 @@ def build_fig_timeline(speakers_dataFrame, currTotalTime, speaker_color_map, get
     )
     fig.update_yaxes(autorange="reversed")
 
-    # Add vertical shading for multi-voice intervals
+    # Add vertical shading for multi-voice intervals.
+    # add_vrect doesn't support hover, so we also add an invisible scatter
+    # trace on top of each band to carry the tooltip.
     MV_COLOR = "#64A377"
     for start_s, end_s in (mv_intervals or []):
+        x0_dt = base + dt.timedelta(seconds=start_s)
+        x1_dt = base + dt.timedelta(seconds=end_s)
         fig.add_vrect(
-            x0=base + dt.timedelta(seconds=start_s),
-            x1=base + dt.timedelta(seconds=end_s),
+            x0=x0_dt, x1=x1_dt,
             fillcolor=MV_COLOR,
-            opacity=0.20,
+            opacity=0.30,
             layer="below",
             line_width=0,
         )
+        # Invisible scatter at midpoint to carry hover tooltip
+        mid_dt = base + dt.timedelta(seconds=(start_s + end_s) / 2)
+        fig.add_trace(go.Scatter(
+            x=[mid_dt],
+            y=[None],
+            mode="markers",
+            marker=dict(size=0, opacity=0),
+            showlegend=False,
+            hovertemplate=(
+                f"<b>Resource: Multi Voice</b><br>"
+                f"Start: {_seconds_to_hhmmss(start_s)}<br>"
+                f"Finish: {_seconds_to_hhmmss(end_s)}"
+                "<extra></extra>"
+            ),
+        ))
 
     h = int(currTotalTime // 3600)
     m = int(currTotalTime %  3600 // 60)