Agent chat
The Stop button now draws a real square. While a turn streams, the composer's action button switches from Send to Stop. That Stop mark was the ■ text glyph, so the font's own metrics decided its size and baseline — it rendered as a small rectangle sitting high in the circle rather than a centered square. It is now a drawn shape at a fixed size with soft corners, exactly centered, on a brighter disc so it reads as the primary action mid-turn.
Behavior is unchanged: clicking it still interrupts the running turn, and the idle Send button is untouched.