swarm-ui: a group pane's maximize and close are icon-only badges in its top right corner

The two controls sat among the pane's header badges as a labelled badge and a
cross glyph. They are now icon badges in the top right corner, through a
`trailing` slot of the terminal preview, so the header on the left keeps the
agent, split, subagents and state badges and a narrow pane wraps less.

docs/swarm/ui.md

@@ -169,11 +169,12 @@ a group of the two, with its own header tab at `/agents/group/<id>`. In a group,
 the same drag onto a pane splits that pane, as many times as you like, and
 dragging a pane's header badge onto another pane moves it there. The **split**
 button in a pane's header does the same for an agent whose terminal tab is open:
-**right** or **below** puts it beside the pane. **maximize** opens that
-agent's own terminal in its tab, or goes to the tab when one is open already. A pane
-can hold a subagent's terminal (its header reads `agent/subagent`), put there by
-the **subagents** badge in the pane's header. The **×** takes the pane's
-agent out of the group, and a group left with one agent goes, landing on that
+**right** or **below** puts it beside the pane. A pane can hold a subagent's
+terminal (its header reads `agent/subagent`), put there by the **subagents**
+badge in the pane's header. Two icon buttons sit in a pane's top right corner.
+**Maximize** (the arrows pointing to the corners) opens that pane's own terminal
+in its tab, or goes to the tab when one is open already. **Close** (the cross)
+takes the pane out of the group, and a group left with one pane goes, landing on that
 agent's own terminal. Drag a divider to resize, or focus it and use the arrow
 keys. Panes have no minimum size; a divider stops at 2% so a pane can't
 vanish.

frontend/packages/shared/src/icons.tsx

@@ -83,6 +83,27 @@ export function ExpandIcon() {
   );
 }
 
+// A cross, for an icon-only close trigger (a pane's "take this out of the
+// group"). Same size and stroke as `ExpandIcon`.
+export function CloseIcon() {
+  return (
+    <svg
+      width="1.3em"
+      height="1.3em"
+      viewBox="0 0 24 24"
+      fill="none"
+      stroke="currentColor"
+      stroke-width="2"
+      stroke-linecap="round"
+      stroke-linejoin="round"
+      aria-hidden="true"
+    >
+      <line x1="5" y1="5" x2="19" y2="19" />
+      <line x1="19" y1="5" x2="5" y2="19" />
+    </svg>
+  );
+}
+
 // A funnel, the standard "filter" glyph — smaller than the other two
 // (1em not 1.3em) since its first caller sits inside a table header
 // cell, not a nav trigger button; scale via the caller's own

frontend/packages/swarm-ui/src/agent/terminal/AgentTermPreview.css

@@ -102,6 +102,12 @@
 .ui-agent-term-preview-controls > * {
   pointer-events: auto;
 }
+/* The icon-only controls in the top right corner. */
+.ui-agent-term-preview-trailing {
+  display: flex;
+  flex: none;
+  gap: 0.25em;
+}
 .ui-agent-term-preview-header-badges {
   display: flex;
   flex-wrap: wrap;

frontend/packages/swarm-ui/src/agent/terminal/AgentTermPreview.tsx

@@ -206,6 +206,7 @@ export function AgentTermPreview({
   subagent,
   fullHeight = false,
   leading,
+  trailing,
 }: {
   agentName: string;
   // Set: this is one of `agentName`'s subagents, output only like the
@@ -217,6 +218,9 @@ export function AgentTermPreview({
   // A badge ahead of the connection badge, for the full-tab mount's
   // link back to the agent's details.
   leading?: ComponentChildren;
+  // Icon-only badges in the top right corner, for the full-tab mount's own
+  // controls (a group pane's maximize and close).
+  trailing?: ComponentChildren;
 }) {
   const paths = termPaths(agentName, subagent);
   const { rows, connection, reconnect } = useSwarmTermStream(paths.stream);
@@ -293,6 +297,9 @@ export function AgentTermPreview({
               onClick={() => openTab({ href: paths.page, label: paths.label })}
             />
           )}
+          {trailing !== undefined && (
+            <div class="ui-agent-term-preview-trailing">{trailing}</div>
+          )}
         </div>
         <div class="live terminal" ref={logRef} onScroll={handleScroll}>
           {rows.length === 0 ? (

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

@@ -2,16 +2,17 @@
 // `/agents/group/:id`: each pane is one agent's full terminal, split by
 // dragging another agent's terminal tab (or a pane's header) onto the edge of
 // a pane, or by the split button in a pane's header. A pane can also be one of
-// an agent's subagents, put beside it by the subagents menu. Dividers resize, and the
-// layout is saved in the browser (`useTermGroups`). A pane's × takes its agent
-// out of the group; a group of one gives way to that agent's own terminal.
+// an agent's subagents, put beside it by the subagents menu. Dividers resize,
+// and the layout is saved in the browser (`useTermGroups`). A pane's close icon
+// takes its agent out of the group, its maximize icon opens the agent on its
+// own; a group of one gives way to that agent's own terminal.
 //
 // Registers its header tab like an agent terminal does, so a reload or a
 // bookmark reopens it. The tab shows the group's name, or its agents.
 import { useEffect } from "preact/hooks";
 import { useLocation, type RouteComponentProps } from "wouter-preact";
 import { Badge } from "@hive/shared/badge.js";
-import { ExpandIcon } from "@hive/shared/icons.js";
+import { CloseIcon, ExpandIcon } from "@hive/shared/icons.js";
 import { AgentIcon } from "../../agent/AgentIcon.js";
 import { SubagentsMenu } from "../../agent/terminal/SubagentsMenu.js";
 import {
@@ -185,10 +186,13 @@ export function AgentGroupPage({
                   )
                 }
               />
+            </>
+          }
+          trailing={
+            <>
               <Badge
-                icon={<ExpandIcon />}
-                value="maximize"
-                title={`open ${key}'s terminal on its own`}
+                value={<ExpandIcon />}
+                title={`maximize: open ${key}'s terminal on its own`}
                 onClick={() =>
                   open({
                     href: termPaths(agent, subagent).page,
@@ -197,9 +201,8 @@ export function AgentGroupPage({
                 }
               />
               <Badge
-                variant="quiet"
-                value="×"
-                title={`take ${key} out of this group`}
+                value={<CloseIcon />}
+                title={`close: take ${key} out of this group`}
                 onClick={() =>
                   groups.update(id, (r) => removeAgent(r, key) ?? r)
                 }