Remove `pendingInterruptAbort = false` from startTurn() and
`queryRestartNeeded = true` from requestCancel(). Both violated the
existing coordination contracts:
- pendingInterruptAbort must only be cleared by the stream pump at its
safe consumption points, not eagerly by the turn lifecycle
- queryRestartNeeded is for transport-level restarts (config changes,
rewind), not for normal interrupt/cancel flows — setting it on every
cancel killed the Claude process and destroyed background tasks
The actual fix for the send-during-tool-call bug was the manager-side
pendingForegroundRun settlement wait added in the previous commit.