PR #1346 - Cadence-Breaker Resilience

Autonomous systems fail in surprisingly ordinary ways: two agents append to the same markdown index, a stalled process spends its budget without changing a file, a harness rejects a startup option, or a dead PID leaves a worktree behind. This change gives each failure a bounded recovery path.

The resilience engine adds a conservative markdown auto-rebaser, a sentinel circuit breaker at 500,000 zero-file tokens or $5, startup failover to the next harness, and an SRE reaper for dead daemon jobs. Recovery is observable: the job state and sentinel telemetry record what happened, while unsupported git conflicts remain fail-closed for human review.

The goal is not to hide failures. It is to keep a routine failure from breaking the cadence of the autonomous loop.