Task: Implement Hotfix handling

Produce three artefacts:

1. doc/llm/runbooks/hotfix/runbook.org — a step-by-step hotfix runbook (extract error → fetch main → create hotfix/ branch → scaffold story/task → diagnose/fix → commit/push/PR). References How do I start a new feature branch phase? for branch mechanics and How do I start a unit of work with compass? for scaffolding.
2. Updated How do I start a new feature branch phase? — adds hotfix/<description> to the * Conventions section and a short note distinguishing hotfix branches from feature branches.
3. Updated v2_doc_sprint.org.mustache — adds a ** Hotfixes section at the end of * Stories, before * Health Review.

• Runbook file exists at doc/llm/runbooks/hotfix/runbook.org.
• Runbook references the branching recipe and compass scaffold recipe by [[id:UUID]] link.
• Branching recipe * Conventions section lists hotfix/<description>.
• Sprint template has ** Hotfixes section with table scaffold.

1. Scaffold runbook with compass add runbook --slug hotfix.
2. Fill runbook body with the hotfix procedure steps.
3. Edit branching recipe to add hotfix convention.
4. Edit sprint template to add ** Hotfixes section.