Add policy-bounded automated OSS maintenance

[ProfesseurHaipeng]

What changed

Adds two independent maintenance skills (English and Chinese), a deterministic policy-driven planner, and narrowly permissioned GitHub Actions workflows for issue triage, PR metadata, and scheduled reporting.

Why

The project needs repeatable maintenance support while preserving maintainer control, explicit policy boundaries, and a safe path for security-sensitive reports.

Maintainer impact

• Default behavior is reviewable metadata maintenance; no content writes or automatic stale-issue closure.
• Sensitive or security-related input is kept out of optional AI enrichment.
• Stale closure remains report-only pending live-state revalidation.
• Documentation explains activation prerequisites and the human-review boundary.

Validation

• python3 -m unittest discover -s automation/tests -v (72 passed)
• Both skills pass the OpenAI skill validator
• git diff --check

Follow-up before enabling optional AI enrichment

Add OPENAI_API_KEY as a repository secret only if a maintainer elects to enable that optional path.