dismiss background task chips one at a time

the tray only had a bulk clear, so getting rid of one finished chip meant
clearing all of them. each finished chip now carries its own close control.

the pill becomes a div wrapping two buttons — a button nested inside a button
is invalid and the browser eats one of the two clicks. running chips stay
undismissable: the tray is the only handle on work still going.

src/workspaces/officerdev/src/apps/Chat/components/BackgroundTaskTray.tsx

@@ -28,7 +28,7 @@ function statusTone(status: BackgroundTask['status']): Tone {
  * tail of a backgrounded shell's log, both read from the file Claude Code streams the task into.
  */
 export const BackgroundTaskTray = ({ messages }: BackgroundTaskTrayProps) => {
-  const { tasks, running, dismissFinished } = useBackgroundTasks(messages);
+  const { tasks, running, dismiss, dismissFinished } = useBackgroundTasks(messages);
   const [openId, setOpenId] = useState<string | null>(null);
 
   // Derived, not stored: dismissing the chip that is open closes the panel without a second piece of state
@@ -54,6 +54,9 @@ export const BackgroundTaskTray = ({ messages }: BackgroundTaskTrayProps) => {
               task={task}
               active={task.taskId === openId}
               onClick={() => setOpenId(task.taskId === openId ? null : task.taskId)}
+              // Finished only. A running chip is the only handle on work still going on, so closing one
+              // would hide something you cannot get back to — the bulk clear draws the same line.
+              onDismiss={task.status ? () => dismiss(task.taskId) : undefined}
             />
           ))}
         </div>
@@ -61,8 +64,8 @@ export const BackgroundTaskTray = ({ messages }: BackgroundTaskTrayProps) => {
           <button
             type="button"
             onClick={dismissFinished}
-            title="Clear finished"
+            title="Clear all finished"
-            aria-label="Clear finished tasks"
+            aria-label="Clear all finished tasks"
             className="shrink-0 cursor-pointer rounded p-1 text-muted-foreground transition-colors hover:bg-muted hover:text-foreground"
           >
             <X className="h-3.5 w-3.5" />
@@ -79,22 +82,31 @@ type TaskChipProps = {
   task: BackgroundTask;
   active: boolean;
   onClick: () => void;
+  /** Absent for a running task — see the call site. */
+  onDismiss?: () => void;
 };
 
-const TaskChip = ({ task, active, onClick }: TaskChipProps) => {
+/**
+ * The pill is a div wrapping two buttons rather than one button with a close control inside it: a button
+ * nested in a button is invalid, and the browser resolves it by swallowing one of the two clicks.
+ */
+const TaskChip = ({ task, active, onClick, onDismiss }: TaskChipProps) => {
   const { status } = task;
   const tone = toneText[statusTone(status)];
 
   return (
-    <button
+    <div
-      type="button"
+      className={`group flex shrink-0 items-center rounded-full border text-xs transition-colors ${
-      onClick={onClick}
-      aria-expanded={active}
-      className={`flex shrink-0 cursor-pointer items-center gap-1.5 rounded-full border px-2.5 py-1 text-xs transition-colors ${
         active
           ? 'border-duck-teal/40 bg-duck-teal/10 text-foreground'
           : 'border-border bg-background/60 text-muted-foreground hover:border-foreground/20 hover:text-foreground'
       }`}
+    >
+      <button
+        type="button"
+        onClick={onClick}
+        aria-expanded={active}
+        className={`flex cursor-pointer items-center gap-1.5 py-1 pl-2.5 ${onDismiss ? 'pr-1' : 'pr-2.5'}`}
       >
         {status === 'completed' ? (
           <Check className={`h-3 w-3 ${tone}`} />
@@ -109,6 +121,20 @@ const TaskChip = ({ task, active, onClick }: TaskChipProps) => {
         )}
         <span className="max-w-[14rem] truncate">{task.description || 'Background task'}</span>
       </button>
+      {onDismiss && (
+        // Always drawn, not revealed on hover: the strip is as much a touch target as a pointer one, and
+        // a control you can only find by hovering is one half the devices cannot find at all.
+        <button
+          type="button"
+          onClick={onDismiss}
+          title="Dismiss"
+          aria-label={`Dismiss ${task.description || 'background task'}`}
+          className="cursor-pointer rounded-full py-1 pl-0.5 pr-2 text-muted-foreground/50 transition-colors hover:text-foreground"
+        >
+          <X className="h-3 w-3" />
+        </button>
+      )}
+    </div>
   );
 };
 

src/workspaces/officerdev/src/apps/Chat/useBackgroundTasks.ts

@@ -56,8 +56,17 @@ export function useBackgroundTasks(messages: ChatMessage[]) {
   return {
     tasks: visible,
     running,
-    /** Clear the finished chips. Running ones are never dismissable — they'd leave nothing watching them. */
+    /**
-    dismissFinished: () => setDismissed(tasks.filter((t) => t.status).map((t) => t.taskId)),
+     * Close one chip. Only ever called for a finished task — running ones are not dismissable, because the
+     * tray is the only thing watching them and a hidden running task is one you have no way back to.
+     *
+     * Dismissing the newest of a capped set promotes the next-oldest into view rather than leaving a gap:
+     * `FINISHED_KEPT` is how many finished chips are shown, not which ones survive.
+     */
+    dismiss: (taskId: string) => setDismissed((prev) => (prev.includes(taskId) ? prev : [...prev, taskId])),
+    /** Clear every finished chip at once. Additive, so chips closed one at a time are not resurrected. */
+    dismissFinished: () =>
+      setDismissed((prev) => [...new Set([...prev, ...tasks.filter((t) => t.status).map((t) => t.taskId)])]),
   };
 }