fix(desktop): stop completed-message layout shift while streaming

The assistant message action bar used `hideWhenRunning`, which unmounts it
whenever the thread is streaming. Since the bar reserves vertical space in
each completed assistant message's footer (it's invisible-until-hover via
opacity, not via mount), unmounting it collapsed every prior turn by the
bar's height — then remounting on resolve grew them back, shifting the whole
conversation (visible as "padding appears above the last user message").
Drop hideWhenRunning so the footer height is constant; the bar stays
invisible during streaming via its existing opacity/pointer-events gating.

apps/desktop/src/components/assistant-ui/thread.tsx

@@ -517,11 +517,17 @@ const AssistantActionBar: FC<MessageActionProps> = ({ messageId, messageText, on
     <div className="relative flex w-full shrink-0 justify-end">
       <ActionBarPrimitive.Root
         className={cn(
+          // NOTE: intentionally NOT `hideWhenRunning`. That prop unmounts the
+          // bar while the thread streams, which collapses every completed
+          // assistant message's footer by this bar's height and shifts the
+          // whole conversation when the turn resolves. The bar is already
+          // invisible by default (opacity-0 + pointer-events-none, reveals on
+          // hover), so keeping it mounted reserves stable layout height with
+          // no visual change during streaming.
           'relative flex flex-row items-center justify-end gap-2 py-1.5 opacity-0 pointer-events-none group-hover:pointer-events-auto group-hover:opacity-100 focus-within:pointer-events-auto focus-within:opacity-100',
           menuOpen && 'pointer-events-auto opacity-100 [&_button]:opacity-100'
         )}
         data-slot="aui_msg-actions"
-        hideWhenRunning
       >
         <CopyButton appearance="icon" buttonSize="icon" disabled={!messageText} label="Copy" text={messageText} />
         <ActionBarPrimitive.Reload asChild>

tools/mcp_tool.py

@@ -1654,10 +1654,10 @@ class MCPServerTask:
                 self.name,
             )
 
-        # Validate remote URL once, up front. Raising here (rather than
+        # Validate remote URL once, up front.  Raising here (rather than
         # letting it blow up inside the SDK's httpx layer on every retry)
         # means a typo in config.yaml fails fast with a clear error — and
-        # critically, no reconnect-backoff burn. (Ported from
+        # critically, no reconnect-backoff burn.  (Ported from
         # anomalyco/opencode#25019.)
         if self._is_http():
             try: