docs: add Tripo H3.1 section to model generation tutorial (en/zh/ja)

[lin-bot23]

Summary

Updates the Tripo model generation tutorial to introduce Tripo H3.1, the latest model version now available through ComfyUI Partner Nodes. Based on the official Tripo H3.1 announcement.

Changes

New section: "What's New in Tripo H3.1" (en/zh/ja)

• High-density geometry for sharper edges and cleaner silhouettes
• PBR-ready material behavior for reliable lighting across render environments
• Hero asset quality stable in close-up shots
• Cross-scenario reuse across game, marketing, and render pipelines
• Typical use cases: game hero assets, marketing visuals, product visualization, 3D printing

Updated model selection documentation (all three sections)

• Added v3.1 as the recommended model version in the parameter description
• Expanded the model list: v3.1 → v3.0 → v2.5 → v2.0 → v1.4 (with descriptions)
• Added "Getting Started with H3.1" guide using Template Library

Get Started guide

• Step-by-step: open Template Library → search "Tripo" → select Tripo3.0 workflow template → set model to v3.1

Closes the need for a separate Tripo H3.1 announcement doc by updating the existing tutorial.

[lin-bot23]

Closing — will create a separate H3.1 page instead