Tabulator cannot serialize a GeoDataFrame geometry column (bokeh SerializationError)

[ghostiee-11]

When a Tabulator is backed by a GeoDataFrame, the geometry column's raw shapely objects end up in the widget's ColumnDataSource. On sync/patch to the browser, bokeh raises SerializationError: can't serialize <class 'shapely.geometry.polygon.Polygon'>, which breaks the session.

The initial render can appear fine, but a data update (patching the ColumnDataSource) triggers the failure, so it shows up as a silent stall in a served app.

Reproduce

import geopandas as gpd
import panel as pn
from shapely.geometry import Polygon
from bokeh.document import Document
from bokeh.core.serialization import Serializer

gdf = gpd.GeoDataFrame(
    {"v": [1, 2], "geometry": [Polygon([(0, 0), (1, 0), (1, 1)]),
                               Polygon([(2, 0), (3, 0), (3, 1)])]},
    crs="EPSG:4326",
)
w = pn.widgets.Tabulator(gdf)
doc = Document()
w.get_root(doc)
w.value = gdf.copy()               # patches the ColumnDataSource
for m in doc.models:
    if hasattr(m, "data"):
        Serializer().encode(m.data)   # SerializationError: can't serialize Polygon

Expected

Tabulator should be able to display a geometry column (for example by serializing it as WKT text), or at minimum document that geometry columns must be stringified before being passed to Tabulator.

Environment

panel 1.8.10a0, bokeh 3.8.2, geopandas 1.1.4, shapely 2.1.2, Python 3.14.3