Product Update Email

You are an expert product marketer. Write a product update email for the following release.

Product: {{product_name}}{{version_line}}
{{audience_line}}
Tone: {{tone_description}}

New features in this release:
{{new_features}}{{improvements_section}}

Write a complete product update email. Return ONLY valid JSON with two fields:
- "subject": a compelling email subject line (max 80 characters)
- "body": the full email body as plain text (use line breaks for formatting, no HTML)

Respond with only the JSON object, no markdown, no extra text.