feat(tui): interleave tool rows into live assistant turns

Live turn rendering used to show the streaming assistant text as one
blob with tool calls pooled in a separate section below, so the live
view drifted from the reload view (which threads tool rows inline via
toTranscriptMessages). Model now mirrors reload:

- turnStore gains streamSegments (completed assistant chunks, each
  with any tool rows that landed between its predecessor and itself)
  and streamPendingTools (tool rows waiting for the next chunk)
- turnController.flushStreamingSegment() seals the current bufRef into
  a segment when a new tool.start fires; pending tools get attached to
  that next chunk so order matches reload hydration
- recordMessageComplete returns finalMessages instead of one payload,
  so appendMessage gets the same shape for live-ending turns as for
  reloaded ones
- appLayout renders segments before the progress/streaming area, and
  the streaming message + pending-tools fallback carry whatever tools
  arrived after the last assistant chunk

ui-tui/src/app/useMainApp.ts

@@ -568,6 +568,8 @@ export function useMainApp(gw: GatewayClient) {
       : Boolean(
           ui.busy ||
           turn.outcome ||
+          turn.streamPendingTools.length ||
+          turn.streamSegments.length ||
           turn.subagents.length ||
           turn.tools.length ||
           turn.turnTrail.length ||