Keeps the contributor's history and current main from its base, but
resolves production to the original PR's accepted behavior: an
agent-authored auto or explicit steer queues behind the active turn
when the live session's activeSteeringInterruptsTools is true.

Dropped from the rewrite: the supportsNonInterruptingAgentSteering
capability, Claude hook-boundary steer delivery with a five second
defer timer, deferToQueue/steeringFallbackOfRunId fallback plumbing,
outbox claim-order exceptions, Stop-time steer revocation, and the
global Claude fixture override in the MCP toolkit test. Agent updates
to a tool-interrupting session arrive as the next turn instead.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>