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-lock.json

@@ -1,12 +1,12 @@
 {
 	"name": "@mariozechner/pi-agent",
-	"version": "0.5.8",
+	"version": "0.5.9",
 	"lockfileVersion": 3,
 	"requires": true,
 	"packages": {
 		"": {
 			"name": "@mariozechner/pi-agent",
-			"version": "0.5.8",
+			"version": "0.5.9",
 			"license": "MIT",
 			"dependencies": {
 				"@mariozechner/tui": "^0.1.1",