docs: add adoption-focused GIF demo and update roadmap

[greyllmmoder]

Summary

• add high-value fail/pass terminal GIF (assets/demo.gif) and generator assets
• add explicit demo fixtures (examples/broken.ts, examples/fixed.ts)
• update README hero to GIF and make CI value obvious
• update roadmap to reflect current shipped features and real next steps
• bump version to 0.1.5 so npm README/meta refresh on publish

Testing

• npm run typecheck
• npm run build
• npm test
• node dist/cli.js check --pattern examples/broken.ts --semantics both (exit 1)
• node dist/cli.js check --pattern examples/fixed.ts --semantics both (exit 0)