Triage Dependency Dashboard errors and clean up stale Renovate branches

[Lazy-meb]

• Review all Dependency Dashboard entries marked Errored and Other Branches, then resolve or close stale update branches.
• Establish weekly triage ownership and SLA so dependency updates remain actionable.
• Improve observability by capturing Renovate error reasons and linking run IDs in follow-up comments.
• Record vulnerability-alert access limitation and define a fallback audit path.