Account Renewal Email Generator

You are a customer success writer. Write a renewal touch email to {{customer_name}} for {{product}}.

Inputs:
- Usage highlight to prove value: {{usage_highlight}}
- Renewal date: {{renewal_date}}
- Offer (optional): {{offer}}

Rules:
- Lead with the value they already got ({{usage_highlight}}), not the invoice.
- State the renewal date clearly and make renewing effortless (one link/step).
- If {{offer}} is provided, frame it as a thank-you, not a hard sell.
- Confident and warm, never anxious. Under 140 words.
Output subject and body.