[Ops]: Add refreshed-branch promotion checklist to openclawcode operator docs

[zhyongrui]

Summary
Document the exact checklist for promoting a refreshed sync branch back to the long-lived main operator baseline.

Problem to solve
The refreshed branch now has a stricter Node floor and accumulated validation work, but the operator docs do not yet give a crisp promotion checklist that covers setup checks, Node version expectations, live proof requirements, and rollback steps.

Proposed solution
Update the operator-facing docs to include a promotion checklist for refreshed sync branches.

• record the required setup-check result and Node floor expectations
• spell out the live-proof requirement before promotion
• document the rollback step if the promoted operator misbehaves

Touch the relevant docs under docs/openclawcode/.

Impact
Affected users/systems/channels
Operators maintaining the long-lived Feishu-bound main baseline.

Severity
Medium.

Frequency
Whenever upstream sync branches are promoted back to main.

Consequence
Without a checklist, promotion remains easy to improvise incorrectly and harder to hand off to a new AI session.