Remove browser-extension package (migrated to separate sitegeist repo)

- Remove packages/browser-extension directory
- Update package.json scripts to remove browser-ext from build and dev
- Extension now lives at https://github.com/badlogic/sitegeist
- Uses file: dependencies to pi-ai and pi-web-ui for development

pi-mono.code-workspace

@@ -7,7 +7,7 @@
 			"path": "../mini-lit"
 		},
 		{
-			"path": "../genai-workshop-new"
+			"path": "../sitegeist"
 		}
 	],
 	"settings": {}