notePressure method
Context-pressure stamp (issue #439): the executor calls this at every
child turn boundary with the estimated request tokens and the
effective window, so task_status can show the wall approaching.
In-memory only, like touch — the next boundary refreshes it.
Implementation
void notePressure(
String id, {
required int estTokens,
required int windowTokens,
}) {
final handle = _handles[id];
if (handle == null) return;
handle.estTokens = estTokens;
handle.windowTokens = windowTokens;
_emit(handle);
}