Fix Poiyomi UV tiling not preserved during conversion

[Copilot]

Poiyomi shaders store UV tiling as a _MainTex_ST Vector4 property rather than Unity's standard texture scale/offset metadata. This causes Material.mainTextureScale/mainTextureOffset to return (1,1)/(0,0), losing UV tiling when converting to Toon Lit or Toon Standard.

Changes

• MaterialBase.cs: Added virtual MainTextureScale/MainTextureOffset properties so shader-specific subclasses can override UV tiling extraction. ConvertToToonLit() and GenerateToonLitImage() now use these instead of Material.mainTextureScale directly. Baker material explicitly sets UV tiling after shader swap.

• PoiyomiMaterial.cs: Overrides MainTextureScale/MainTextureOffset to read from Material.GetVector("_MainTex_ST") with fallback to standard API. Fixed stale doc comment.

• LilToonMaterial.cs: Updated existing MainTextureScale/MainTextureOffset properties to use override keyword, fixing CS0114/CS0108 member hiding warnings caused by the new virtual members on MaterialBase.

• PoiyomiMaterialTests.cs: Tests for scale/offset extraction from _MainTex_ST, preservation through ConvertToToonLit(), and non-uniform tiling values.

// PoiyomiMaterial reads UV tiling from the Vector4 property
private Vector4 GetMainTexST()
{
    if (Material.HasProperty("_MainTex_ST"))
    {
        return Material.GetVector("_MainTex_ST");
    }
    var scale = Material.mainTextureScale;
    var offset = Material.mainTextureOffset;
    return new Vector4(scale.x, scale.y, offset.x, offset.y);
}

Original prompt

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This section details on the original issue you should resolve

<issue_title>Fix: Poiyomi UV Tiling not preserved during conversion</issue_title>
<issue_description>### タスク概要

PoiyomiマテリアルをToon LitやToon Standardへ変換した際に、UVタイル（mainTextureScaleおよびmainTextureOffsetなど）が正しく引き継がれない問題の修正。

背景・目的

PoiyomiシェーダでmainTextureScale/mainTextureOffsetがデフォルト（1,1）に戻されてしまい、アバターやメッシュの見た目が損なわれる。Poiyomiの独自プロパティから正しいタイル値を取得し、変換マテリアルに反映する必要がある。

技術要件

• Poiyomiのメインテクスチャのスケール・オフセットが変換後も維持されていること
• lilToonと同様にMaterialWrapper等を抽象化・リファクタして汎用的なUVタイル抽出処理を追加
• PoiyomiのUVタイルを格納するプロパティ（例: _MainTex_STや独自パラメータ）から正確に取得
• 自動テスト追加：X:1, Y:1以外のタイル値を含むケース
• Bake処理にも正しいスケール/オフセットが反映されること

補足情報

• 親Issue: UV Tiling Not Translated #217
• パス: Editor/Models/Unity/PoiyomiMaterial.cs, Editor/Models/Unity/MaterialBase.cs, Shader/vqt_poiyomi.shader
• アセット例: Mitsumame(https://booth.pm/en/items/5748454), Poiyomi(9.3.64)
• Poiyomi独自のUVタイル取得方法に注意
• Poiyomi インストール方法

  vrc-get repo add https://poiyomi.github.io/vpm/index.json
  vrc-get install com.poiyomi.toon

• Packages/packages-lock.json, Packages/vpm-manifest.json, ProjectSettings/* をコミットしないこと

完了条件

• Poiyomiマテリアル変換時に、UVタイル（スケール・オフセット）が正しく反映されていることを手動・自動テストで確認
• 親Issueの再現手順例で問題が再発しないこと</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Fix: Poiyomi UV Tiling not preserved during conversion #220

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[Copilot]

Pull request overview

This PR improves Toon Lit material conversion for Poiyomi materials by correctly preserving main texture UV tiling (including Poiyomi’s _MainTex_ST storage) and avoiding double-tiling when baking textures. It also extends CI to install Poiyomi so the new tests can run.

Changes:

• Add Poiyomi import detection and Poiyomi-specific UV tiling extraction from _MainTex_ST.
• Update Toon Lit conversion/baking flow to apply UV tiling on the output material while baking with identity tiling (prevents double-tiling).
• Add Poiyomi-focused editor tests and update CI workflow to include the Poiyomi VPM repo/package.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Packages/com.github.kurotu.vrc-quest-tools/Editor/Utils/AssetUtility.cs	Adds IsPoiyomiImported() helper for conditional Poiyomi behavior/tests.
Packages/com.github.kurotu.vrc-quest-tools/Editor/Models/Unity/PoiyomiMaterial.cs	Reads UV tiling from _MainTex_ST and exposes it via overrides.
Packages/com.github.kurotu.vrc-quest-tools/Editor/Models/Unity/MaterialBase.cs	Introduces virtual UV tiling accessors; resets bake-time tiling to avoid embedding.
Assets/VRCQuestTools-Tests/Editor/Models/Unity/PoiyomiMaterialTests.cs (+ .meta)	Adds unit tests for _MainTex_ST tiling extraction and Toon Lit conversion preservation.
Assets/VRCQuestTools-Tests/Editor/Models/MaterialGenerators/PoiyomiToonLitGeneratorTests.cs (+ .meta)	Adds generator-level tests ensuring baking preserves scale/offset but doesn’t embed tiling into pixels.
.github/workflows/build.yml	Adds Poiyomi VPM repo and includes com.poiyomi.toon in the “latest deps” test matrix entry.

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