Implement Boot-Time Pre-Flight and Hard-Refusal Predicate for Sandman Handoff

Context During the review of PR #11178 (which automates the active PR cycle state extraction into sandman_handoff.md), the swarm requested narrowing the scope. AC4 (boot-time pre-flight) and AC5 (hard-refusal predicate) were deferred to ensure the base extraction logic could be merged quickly without introducing complex new boot constraints simultaneously.

The Problem While sandman_handoff.md now contains the active PR cycle state, nightshift agents do not automatically enforce behavior based on this state upon booting. Without a boot-time pre-flight and hard-refusal predicate, an agent could pick up a new task or open a new PR while a parallel PR is still waiting on peer review, risking duplicate PRs or collision.

The Architectural Reality The runSandman pipeline now reliably deposits the GoldenPath and PR metadata into resources/content/sandman_handoff.md. The agent's boot sequence (likely integrated into the Mailbox Check Protocol AGENTS.md §22 or a new Pre-Flight step) must be updated to consume this artifact and evaluate the lane-state string.

The Fix

1. Implement a Boot-Time Pre-Flight step that parses resources/content/sandman_handoff.md.
2. Implement a Hard-Refusal Predicate: If the lane-state is AWAITING_REVIEW, AWAITING_HUMAN, or similar blocked state, the agent must halt execution of any new ticket intake or PR creation until the blocking state is resolved (or explicitly overridden by the operator).

Acceptance Criteria

• Agent startup sequence natively reads sandman_handoff.md prior to executing any workflow skills.
• Hard-refusal predicate triggers if an active, blocking lane-state is detected, halting new task execution.
• Clear logging/messaging indicates the blocked state to the operator.

Out of Scope

• Generation of the sandman_handoff.md file itself (handled by PR #11178).

Origin Session ID: 57502eb2-7f7b-4b9b-a849-49f016b08c95