Enhance Agent with Planning and Function Calls Support

[majidmanzarpour]

This PR enhances the Three.js editor's Agent with the following improvements:

Key Features

• Planning Phase: Added a two-phase approach where the agent first plans the 3D model creation before execution
• Function Call Support: Improved handling of GoogleGenAI SDK function calls
• Enhanced Error Handling: Added robust error detection and recovery for API calls

Technical Details

• Updated content formatting to meet the SDK's requirements
• Added debugging to assist with troubleshooting API interactions
• Improved response extraction from the Google GenAI API

These changes make the agent more reliable and capable of handling complex 3D model creation requests through a structured planning and execution approach.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.08 78.29	336.08 78.29	+0 B +0 B
WebGPU	525.21 146.28	525.17 146.28	-40 B +5 B
WebGPU Nodes	524.67 146.18	524.63 146.18	-40 B +5 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.15 112.18	465.15 112.18	+0 B +0 B
WebGPU	598.01 162.57	597.97 162.56	-40 B -7 B
WebGPU Nodes	553.1 152.04	553.1 152.04	+0 B +0 B