Replace object spread (`{...props}`) with `mergeProps` when forwarding
props through the plugin Slot wrapper. Spreading props in SolidJS
evaluates each prop once at mount time, freezing reactive values like
`ref`, `visible`, `disabled`, and `on_submit`. This caused handlers to
bind against stale closures after overlay transitions, breaking Enter
submission on the session_prompt slot.
Add regression tests verifying the wrapper uses `mergeProps` (not
spread) and that reactive prop tracking is preserved at runtime.
Imanol Maiztegui
07024a0341