v0.1.0: Price indicators, per-skill models, Gemini fixes, no code splitting

- Model dropdown shows cost tier ($-$$$$) next to each model
- Skills can store a preferred model (auto-switches on invoke)
- Default priority: Gemini Flash > Haiku > Groq > OpenAI > others
- Gemini: fix type array rejection, empty enum values, model IDs
- Disable webpack code splitting (CSP + publicPath issues in WP admin)
- Model and max tokens persisted in localStorage
- README: added user-facing feature overview

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>