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/AgentsPage.tsx

@@ -35,6 +35,7 @@ import { AgentTermPreview } from "./AgentTermPreview.js";
 import { SubagentTerms } from "./SubagentTerms.js";
 import { FRESHNESS, type AgentRow } from "./AgentTypes.js";
 import { LinkedAccounts } from "./LinkedAccounts.js";
+import { LinkAccountMenu } from "./LinkAccountMenu.js";
 import { Button } from "../../ui/button/Button.js";
 import { ConfirmDialog } from "../../ui/confirm-dialog/ConfirmDialog.js";
 import { Dialog } from "../../ui/dialog/Dialog.js";
@@ -602,53 +603,14 @@ export function AgentsPage() {
                   </dd>
                 </dl>
                 <div class="ui-agent-detail-actions">
-                  <Badge
-                    variant="quiet"
-                    icon={<LinkIcon />}
-                    value="link matrix account"
-                    onClick={
-                      detailTarget.hive
-                        ? () => setMatrixTarget(detailTarget)
-                        : undefined
-                    }
-                    disabled={!detailTarget.hive}
-                    title={
-                      detailTarget.hive
-                        ? `link a matrix account to ${detailTarget.name}`
-                        : "no hive on record for this agent — nothing to link against"
-                    }
-                  />
-                  <Badge
-                    variant="quiet"
-                    icon={<LinkIcon />}
-                    value="link forge account"
-                    onClick={
-                      detailTarget.hive
-                        ? () => setForgeTarget(detailTarget)
-                        : undefined
-                    }
-                    disabled={!detailTarget.hive}
-                    title={
-                      detailTarget.hive
-                        ? `link an external forge account to ${detailTarget.name}`
-                        : "no hive on record for this agent — nothing to link against"
-                    }
-                  />
-                  <Badge
-                    variant="quiet"
-                    icon={<LinkIcon />}
-                    value="link github account"
-                    onClick={
-                      detailTarget.hive
-                        ? () => setGithubTarget(detailTarget)
-                        : undefined
-                    }
-                    disabled={!detailTarget.hive}
-                    title={
-                      detailTarget.hive
-                        ? `link a github account to ${detailTarget.name}`
-                        : "no hive on record for this agent — nothing to link against"
-                    }
+                  <LinkAccountMenu
+                    agent={detailTarget.name}
+                    hasHive={detailTarget.hive !== null}
+                    onSelect={(kind) => {
+                      if (kind === "matrix") setMatrixTarget(detailTarget);
+                      else if (kind === "forge") setForgeTarget(detailTarget);
+                      else setGithubTarget(detailTarget);
+                    }}
                   />
                 </div>
                 {/* The agent's live terminal and its input box. */}

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

@@ -0,0 +1,60 @@
+// <LinkAccountMenu> — one "link account" badge that opens a `Dropdown` with
+// the three kinds of account an agent can be linked to, in place of one
+// badge per kind: three side-by-side badges were wider than the detail
+// panel and spilled out of it. Presentational only, same split as
+// `WantedMenu`: the caller owns what each selection opens.
+import { useRef, useState } from "preact/hooks";
+import { Badge } from "@hive/shared/badge.js";
+import { Dropdown, type DropdownOption } from "@hive/shared/dropdown.js";
+import { LinkIcon } from "@hive/shared/icons.js";
+
+export type LinkKind = "matrix" | "forge" | "github";
+
+const OPTIONS: DropdownOption[] = [
+  { value: "matrix", label: "matrix account" },
+  { value: "forge", label: "forge account" },
+  { value: "github", label: "github account" },
+];
+
+export function LinkAccountMenu({
+  agent,
+  hasHive,
+  onSelect,
+}: {
+  agent: string;
+  /** Linking writes against the agent's hive, so without one there is
+   * nothing to link against and the menu stays shut. */
+  hasHive: boolean;
+  onSelect: (kind: LinkKind) => void;
+}) {
+  const [open, setOpen] = useState(false);
+  const anchorRef = useRef<HTMLDivElement>(null);
+  return (
+    <div class="ui-dropdown-anchor" ref={anchorRef}>
+      <Badge
+        variant="quiet"
+        icon={<LinkIcon />}
+        value="link account"
+        onClick={hasHive ? () => setOpen((o) => !o) : undefined}
+        expanded={open}
+        disabled={!hasHive}
+        title={
+          hasHive
+            ? `link a matrix, forge or github account to ${agent}`
+            : "no hive on record for this agent — nothing to link against"
+        }
+      />
+      <Dropdown
+        open={open}
+        options={OPTIONS}
+        label={`link an account to ${agent}`}
+        onSelect={(value) => {
+          setOpen(false);
+          onSelect(value as LinkKind);
+        }}
+        onClose={() => setOpen(false)}
+        anchorRef={anchorRef}
+      />
+    </div>
+  );
+}

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

@@ -11,7 +11,6 @@
   gap: 0.5em;
 }
 
-.ui-subagent-terms-heading,
-.ui-subagent-terms-empty {
+.ui-subagent-terms-heading {
   color: var(--muted);
 }

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}