Per @steipete review on #68310: the silent-error retry must not fire when the
failed attempt already recorded potential side effects (messaging tool sent,
cron add, or a mutating tool call that wasn't round-tripped as replay-safe).
Otherwise resubmission can duplicate those actions.
Adds `!attempt.replayMetadata.hadPotentialSideEffects` to the retry condition,
mirroring the gate used by resolveEmptyResponseRetryInstruction and the
planning-only / reasoning-only retry resolvers in run/incomplete-turn.ts.
Adds a new negative regression test:
"does not retry when the failed attempt recorded side effects"
which reproduces the reviewer's repro — stopReason=error + output=0 + empty
content, but replayMetadata={hadPotentialSideEffects: true, replaySafe: false}.
Expected: no retry, surfaces incomplete-turn error. Confirmed locally.
dcb525de50