docs: add a personal operator runbook

[DevSecNinja]

Why

The project is GitHub-native and personal, so a small runbook would make it easier to operate without rediscovering workflow commands or recovery steps from chat history.

Scope

• Document normal operations: generate manually, watch a run, validate data, run Pages deployment, inspect source health.
• Document recovery paths: missed schedule, failed provider, broken state asset, bad generated data, source outage.
• Include local development commands and GitHub CLI commands that are already used in practice.
• Keep it short and personal-project friendly.

Acceptance criteria

• There is a concise runbook under docs/.
• Manual catch-up and state validation steps are easy to follow.
• Commands match the current Task/mise workflow.