Improve README description for AI agent features

Rephrase description for clarity and conciseness.

chore: bump version to 1.2.3

- Update version in plugin.json from 1.2.1 to 1.2.3
- Update version in marketplace.json from 1.2.1 to 1.2.3

🤖 Generated with Claude via commitment

Update README with badge links and license info

1.2.1

1.2.0

adjust some wording for consistency; add init command to manage deps;…

… add README