feat(ai): Rename package to @mariozechner/pi-ai and improve documentation

- Changed package name from @mariozechner/ai to @mariozechner/pi-ai
- Fixed generate-models.ts to fetch from models.dev API instead of local file
- Completely rewrote README with practical examples:
  - Image input with base64 encoding
  - Proper tool calling with context management
  - Streaming with completion indicators
  - Abort signal usage
  - Provider-specific options (reasoning/thinking)
  - Custom model definitions for local/self-hosted LLMs
  - Environment variables explanation
- Bumped version to 0.5.9 and published

packages/agent/package.json

@@ -1,6 +1,6 @@
 {
 	"name": "@mariozechner/pi-agent",
-	"version": "0.5.8",
+	"version": "0.5.9",
 	"description": "General-purpose agent with tool calling and session persistence",
 	"type": "module",
 	"bin": {
@@ -18,7 +18,7 @@
 		"prepublishOnly": "npm run clean && npm run build"
 	},
 	"dependencies": {
-		"@mariozechner/pi-tui": "^0.5.8",
+		"@mariozechner/pi-tui": "^0.5.9",
 		"@types/glob": "^8.1.0",
 		"chalk": "^5.5.0",
 		"glob": "^11.0.3",