Drag links out of slots on the wiresheet; hide @palette=false types

Hovering a slot row highlights the half under the pointer and shows a
direction cursor. Pressing on a slot drags a rubber band; dropping on
another slot links them, dropping on a title bar opens the Link dialog
with the dragged slot preselected, and a no-entry cursor marks a slot
that would refuse the link. A right click that never moves still opens
the context menu.

The palette now leaves out types whose facets carry @palette=false, and
kits with nothing placeable left.

Also points the default device host at 192.168.1.251.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

wiresheet.py

@@ -948,6 +948,7 @@ def render_components(components_to_render):
 
     canvas.delete("component")
     canvas.delete("link")
+    canvas.delete("slot_hover")   # link_drag's hover ring, stale once boxes repaint
     app_state.canvas_comp_map.clear()
     app_state.canvas_tag_by_element.clear()
     app_state.component_slot_offsets.clear()