Add site-picker dropdown as robust fallback for click selection

notebook.py

@@ -90,9 +90,17 @@ def _(df, mo):
         show_value=True,
     )
     show_trend = mo.ui.checkbox(value=True, label="Show trend line (Visual 2)")
+    site_picker = mo.ui.dropdown(
+        options=["(click a point in Visual 1)"] + df.site_id.tolist(),
+        value="(click a point in Visual 1)",
+        label="Selected site",
+    )
 
-    mo.hstack([region_filter, dominance_range, show_trend], justify="start", gap=2)
-    return dominance_range, region_filter, show_trend
+    mo.hstack(
+        [region_filter, dominance_range, show_trend, site_picker],
+        justify="start", gap=2,
+    )
+    return dominance_range, region_filter, show_trend, site_picker
 
 
 @app.cell
@@ -181,11 +189,19 @@ def _(pd):
 
 
 @app.cell
-def _(alt, chart1, mo, pd):
+def _(alt, chart1, df, mo, pd, site_picker):
     # --- Linked species breakdown for the selected site(s) ---
-    sel = chart1.value  # pandas DataFrame of currently selected rows
+    # Prefer the dropdown picker; fall back to the scatter click selection.
+    picked = site_picker.value
+    if picked and picked != "(click a point in Visual 1)":
+        sel = df[df.site_id == picked]
+    else:
+        sel = chart1.value  # pandas DataFrame of currently selected rows
     if sel is None or len(sel) == 0:
-        detail_md = mo.md("*Click a point in the scatter above to see the site's species composition.*")
+        detail_md = mo.md(
+            "*Click a point in the scatter above **or** pick one from the "
+            "\"Selected site\" dropdown at the top to see the site's species composition.*"
+        )
         detail = detail_md
     else:
         site = sel.iloc[0]