feat: add first-class Workers AI support

[paoloanzn]

Summary

• add first-class Workers AI binding support to project and Wrangler config models
• add AI binding management commands and new AI scaffolds for chat, vision, speech-to-text, text-to-speech, image generation, and embeddings
• split the AI scaffolding into focused files and fix missing query-param handling for AI requests

Testing

• go test ./...
• live local smoke tests for ai-chat, ai-vision, ai-embeddings, ai-stt, ai-tts, and ai-image via wrangler dev
• verified ai-text shares the ai-chat scaffold path