This eliminates a "bounce" at the end of streaming where we hide the
status indicator at the end of the turn and the composer moves up two
lines.
Also, simplify streaming further by removing the HistorySink and
inverting control, and collapsing a few single-element structures.
Sometimes COT is returns as text content instead of `ReasoningText`. We
should parse it but not serialize back on requests.
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Co-authored-by: Ahmed Ibrahim <aibrahim@openai.com>
Wait for newlines, then render markdown on a line by line basis. Word wrap it for the current terminal size and then spit it out line by line into the UI. Also adds tests and fixes some UI regressions.
