Add content quality scorecard

[contentincubator2-ops]

Summary

Create a lightweight scorecard for evaluating content quality before and after publishing.

Why

The public repo should help people learn what strong positioning-based content looks like, not just help them produce more assets.

Scope

• define 5-8 quality dimensions
• include a simple scoring template
• separate message quality from vanity metrics
• include guidance for weekly review

Acceptance criteria

• scorecard is documented as a reusable template
• it is easy for a small team to use weekly
• it clearly supports the positioning -> execution workflow

Reference

• docs/roadmap.md#phase-3--evaluation-and-iteration-layer