Reassure users while the picker loads more rows

The streaming picker footer read "⏳ loading more <noun>…" during the
background walk, which can read like a hang. Reword it to "⏳ Loading more
<noun>, this might take a few seconds..." so the wait reads as expected.
All three pickers (skills, skill schemas, MCP services) share this footer.

Co-authored-by: Isaac <no-reply@databricks.com>

Author: xsh310

src/ucode/ui/interactive_picker.py

@@ -136,7 +136,7 @@ def scrolling_checkbox(
     on screen: it's run on a daemon thread and handed an ``append(choices)`` callback that
     adds rows (deduped by value) and repaints, so the picker opens instantly on whatever
     ``choices`` are ready and fills in the rest without blocking. A footer shows a live
-    "loading more {loading_noun}…" count while it runs.
+    "Loading more {loading_noun}, this might take a few seconds..." count while it runs.
 
     ``show_description`` adds a footer previewing the highlighted row's ``Choice.description``.
     It's a separate window rather than questionary's inline ``show_description`` because the
@@ -188,7 +188,8 @@ def loading_tokens() -> list[tuple[str, str]]:
             return [
                 (
                     "class:instruction",
-                    f"  ⏳ loading more {loading_noun}… ({loading['found']} found)",
+                    f"  ⏳ Loading more {loading_noun}, this might take a few seconds..."
+                    f" ({loading['found']} found)",
                 )
             ]
         return [("class:instruction", f"  {loading['message']}")]