Fixes#2713 — live assistant text can truncate at tool-call segment
boundaries during streaming.
Before _resetAssistantSegment() in the tool and interim_assistant SSE
handlers, synchronously flush any pending rAF render work so tokens that
arrived during the 66ms throttle window are written to the DOM before
assistantBody is cleared. Without this flush, the pending _doRender
callback fires after assistantBody is null and skips the write silently,
causing the tail of the pre-tool segment to disappear from the live view.
Implementation:
- Extract _flushPendingSegmentRender() helper (guarded by assistantBody
&& _renderPending) that cancels the pending rAF and synchronously
writes via smd/renderMd/esc — same cascade as _doRender.
- Call the helper from both the tool and interim_assistant handlers
before their respective _resetAssistantSegment() calls.
- Normal cases where the rAF has already fired are unaffected (guard
skips immediately).
Completed transcripts were never affected (renderMessages rebuilds from
the full assistantText accumulator on done).
Adds tests/test_issue2713_streaming_segment_flush.py with 11 static
analysis regression tests pinning the helper shape and call-site
ordering.
