Update System Template

Update a system-org template's settings, goals, name, or description (admin-only).

Body keys (all optional):

• settings: dict — merged into existing settings (shallow merge per top-level key)
• goals: list — REPLACES the existing goals array entirely
• name: str
• description: str

For CHILD templates (parent_template_id IS NOT NULL): inherited fields are read-only and PATCH attempts to change them return 422. Allowed: name, description, status, settings.skills (additive list).