* fix(cache): compact newest tool results first to preserve prompt cache prefix
compactExistingToolResultsInPlace iterated front-to-back, replacing the
oldest tool results with placeholders when context exceeded 75%. This
rewrote messages[k] for small k, invalidating the provider prompt cache
from that point onward on every subsequent turn.
Reverse the loop to compact newest-first. The cached prefix stays intact;
the tradeoff is the model loses recent tool output instead of old, which
is acceptable since this guard only fires as an emergency measure past
the 75% threshold.
* fix(cache): compact newest tool results first to preserve prompt cache prefix (#58036) Thanks @bcherny
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Co-authored-by: George Zhang <georgezhangtj97@gmail.com>
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