_aser_component expands component bodies in SX wire format mode,
but was evaluating kwarg values with async_eval (HTML mode). This
caused SxExpr kwargs to be fully rendered to HTML strings, which
then broke when serialized back to SX — producing bare symbols
like 'div' that the client couldn't resolve.
Fix: use _aser() for kwarg evaluation to keep values in SX format.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>