Auto modes collapse and PolicyEngine reaches into ACP sessions

What this changes for operators

• Operators on previous Auto variants must re-audit which behaviors the consolidated Auto mode treats as safe — the merger may have loosened or tightened constraints; release notes do not enumerate.
• AUTO_EDIT operators should explicitly decide whether shell-redirect auto-approval is acceptable for their environment.
• Operators evaluating Gemini ACP integration should treat PolicyEngine-in-ACP as the new enforcement boundary; the 'deadlock fix' framing understates the structural shift.