Fix grade chart needing double-click to display

Remove fixed y-axis range and override hovermode to "closest" for
categorical bar charts — template's "x unified" hovermode caused
Plotly to initialize with a bad viewport on categorical axes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app.py

@@ -693,7 +693,7 @@ elif selected_view == "Design":
         text=[f"{v:.1f}%" for v in grades_df["Percentage"]],
         textposition="outside",
     ))
-    fig_grades.update_layout(title="Return Grade Distribution", yaxis_title="% of Returns", yaxis=dict(range=[0, 105]))
+    fig_grades.update_layout(title="Return Grade Distribution", yaxis_title="% of Returns", hovermode="closest")
     st.plotly_chart(fig_grades, use_container_width=True)
 
     st.info(f"**Design insight:** At {st.session_state.design_damage_rate}% damage rate with repairability score "
@@ -846,7 +846,7 @@ elif selected_view == "Logistics":
             text=[f"{v:.0f}%" for v in grades_df["Percentage"]],
             textposition="outside",
         ))
-        fig_grades.update_layout(title="Return Grade Distribution", yaxis_title="% of Returns")
+        fig_grades.update_layout(title="Return Grade Distribution", yaxis_title="% of Returns", hovermode="closest")
         st.plotly_chart(fig_grades, use_container_width=True)
 
     with grade_col2: