swarm-ui: one link-account menu, and no subagents section without subagents

The three link-account badges were wider than the agent detail panel and
spilled out of it; they are now a single badge opening a dropdown of the
three kinds. The subagents row, heading included, is not rendered for an
agent that has none.

frontend/packages/swarm-ui/src/pages/agents/SubagentTerms.tsx

@@ -37,16 +37,15 @@ export function SubagentTerms({ agentName }: { agentName: string }) {
     refresh().catch((e: unknown) => setError({ detail: String(e) }));
   });
 
+  // An agent with no subagents shows nothing here — no heading, no
+  // "none" line — and so does the first fetch while it is in flight. A
+  // failed fetch still shows, so the error is not swallowed.
+  if (!error && (names === null || names.length === 0)) return null;
+
   return (
     <section class="ui-subagent-terms" aria-label={`${agentName}'s subagents`}>
       <div class="ui-subagent-terms-list">
         <span class="ui-subagent-terms-heading">subagents</span>
-        {names === null && !error && <Badge value="loading…" />}
-        {names?.length === 0 && (
-          <span class="ui-subagent-terms-empty">
-            none with output on record
-          </span>
-        )}
         {names?.map((name) => (
           <Badge
             key={name}