Add an independent GitHub delivery watchdog with guarded merge

[neubig]

Desired Behavior

Add a separate scheduled automation that identifies blocked delivery, reports required next actions, and automatically merges accepted current-head changes. Use the selected watchdog agent profile and repository-scoped GitHub token. Reuse native GitHub statuses and Actions for the acceptance gate; never implement or review application code.

Acceptance Criteria

• Independently configurable automation catalog entry with its own implementation and schedule.
• Agent profile is persisted on the automation and is the source of agent settings and available secrets.
• No github-software-factory role-switched runner is required.
• Focused tests plus live validation on the existing Airbnb demo; application changes remain automation-only.
• Replace the relevant parts of feat(factory): compose canonical implementation, review, QA, and guarded merge #557/feat: run independent factory issues in bounded developer lanes #564 and document review dependencies.

[github-actions]

✅ ready-for-dev label applied

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