Take the terminal loop that paints only when the tree moved

jolt-native's terminal backend laid out and painted the whole tree every
tick, sixty times a second, whether or not anything had changed. An frq
conversation sitting idle in a terminal cost most of a core for it, and
the several left open around a working day cost one each.

Upstream now sets a flag in the five backend operations every reconciler
change passes through, and paints when it is set — `tick` already blocks
for up to a frame waiting for input, so the loop sleeps there instead of
spinning. Measured here on the demo screen, untouched: 134% of a core
becomes 7.9%.

Nothing on this side changes. The headless screenshot is the same bytes
it was, tag for tag, which is the check that says the frames not painted
were the frames that would have painted nothing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>