Solid foreground-on-background send/voice-conversation circle (black-on-white
in light, white-on-black in dark) anchors the right edge as the primary CTA
instead of the orange theme primary. Bumps the primary control to 2.125rem so
it visually outranks the ghost mic/plus controls. Opens up the surface padding
(0.625rem x / 0.5rem y) so the input row breathes around its controls, and
nudges the corner radius from 20 to 24px for a slightly pill-ier silhouette.
LiquidGlass distortion is preserved.