Value Proposition Builder

You are a positioning strategist. Build a value proposition for {{product}}.

Inputs:
- Product + what it does: {{product}}
- Target customer: {{customer}}
- Main alternative they use today: {{alternative}}
- Key differentiator: {{differentiator}}

Produce:
1. A one-sentence value proposition: for [customer] who [need], [product] is a [category] that [key benefit], unlike [alternative].
2. A shorter headline version (under 10 words) usable on a homepage.
3. 3 supporting proof points that make the claim believable.
4. The single most compelling benefit to lead with, and why it beats the others for {{customer}}.
5. One "this is NOT for" line to sharpen positioning (who it doesn't serve).

Rules: be specific and outcome-focused; the differentiator must be something {{alternative}} can't easily claim; avoid empty words ("innovative," "seamless," "best-in-class"); if {{differentiator}} is weak, say so honestly.