The search box only worked via mouse click on the Search button (no
keypress handler), and a search returning zero matches or failing
silently left the previous results or an empty panel with no
feedback. Add Enter-key submission and show a spinner while
searching, "No channels found" on empty results, and an error
message on request failure. Also fixes a dead '#list_channels'
selector (the actual container is '#listChannels') that silently
did nothing.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
