fix(tui): don't clobber busy on the progress panel during streaming

`appLayout` was passing `busy={ui.busy && !progress.streaming}` into
ToolTrail, so the moment `message.delta` fired and streaming began,
the panel internally saw `busy=false`. With the prior fix in place
(hasThinking = !!cot || reasoningActive || busy), that flipped
hasThinking to false and the Thinking expander vanished mid-turn —
reappearing only after message.complete when the finalized row
rendered with its own internal expander.

The `!progress.streaming` override was a defensive guard against the
panel implying "still thinking" once the response text was streaming.
But that's already handled inside ToolTrail — `streaming` prop on the
Thinking component uses `busy && reasoningStreaming`, and
reasoningStreaming is already falsey once recordMessageDelta calls
endReasoningPhase.

Pass plain `busy={ui.busy}`. Panel stays up start-to-finish; handoff
to the finalized-message row is continuous.

ui-tui/src/components/appLayout.tsx

@@ -58,7 +58,7 @@ const TranscriptPane = memo(function TranscriptPane({
           {progress.showProgressArea && (
             <ToolTrail
               activity={progress.activity}
-              busy={ui.busy && !progress.streaming}
+              busy={ui.busy}
               detailsMode={ui.detailsMode}
               reasoning={progress.reasoning}
               reasoningActive={progress.reasoningActive}