Add DiffSinger variance local pitch patch

[KakaruHayate]

解决的问题

原始行为中，用户修改 pitch 后，DiffSinger variance model 会重新生成整段 variance 曲线。由于 variance model 输出存在一定随机性或全局联动，未被用户修改的 pitch 区域也可能发生变化，这会偏离用户预期。

本改动提供一个默认关闭的新选项：只在用户开启后，对 pitch 发生变化的区域应用新的 variance 输出，未变化区域保留上一次结果。

核心逻辑

• 新增 DiffSinger 专用的局部 patch 逻辑。
• 通过缓存前后两次 variance model 的 pitch 输入数组，比较得到 pitch 发生变化的帧范围。
• variance model 仍然完整运行一次，不修改 ONNX 输入构建，也不使用无效的 retake 输入。
• 输出阶段只把变化范围附近的新 variance 曲线拼接进旧结果。
• 拼接边界使用短交叉淡化，避免明显断点。
• 如果没有历史状态、长度/metadata 不一致、合并异常等情况，自动 fallback 到原始完整 variance 结果。

开关与约束

• 新选项默认关闭：DiffSingerVarianceLocalPitchPatch = false

• 该功能依赖 DiffSinger Tensor Cache。

• 当 DiffSingerTensorCache 未开启时：

  • UI 中该选项不可用。
  • 运行时也不会启用局部 patch。

• 这样可以避免在无缓存状态下引入不稳定行为。

改动文件

• OpenUtau.Core/DiffSinger/DiffSingerVariance.cs

  • 接入局部 variance patch。
  • 构建不含 pitch 的 patch key。
  • 在 variance 输出后执行局部合并。
  • 保留失败 fallback。

• OpenUtau.Core/DiffSinger/DiffSingerVariancePatch.cs

  • 新增 DiffSinger variance 局部合并 helper。
  • 包含 pitch 差异范围检测、权重生成、交叉淡化、结果 clone/fallback。

• OpenUtau.Core/Util/Preferences.cs

  • 新增默认关闭的偏好项。

• OpenUtau/ViewModels/PreferencesViewModel.cs

  • 新增偏好项绑定与保存逻辑。

• OpenUtau/Views/PreferencesDialog.axaml

  • 在 DiffSinger 设置区新增开关。
  • 开关受 DiffSingerTensorCache 启用状态控制。

• OpenUtau/Strings/Strings.axaml

  • 新增英文资源键。
  • 中文资源因编码环境不确定，本次未修改，后续可补。

• OpenUtau.Core/Properties/AssemblyInfo.cs

  • 新增测试程序集 internal 可见性，保持 patch helper 不暴露为公开 API。

• OpenUtau.Test/Core/DiffSinger/DiffSingerVariancePatchTest.cs

  • 覆盖 pitch 改动范围检测、无 pitch 改动保留旧结果、局部 blend、metadata 不一致 fallback。

[Copilot]

Pull request overview

This PR adds an optional (default-off) DiffSinger “local variance patch” behavior so that when a user edits pitch, the variance model still runs normally but only the pitch-changed frame ranges are merged into the previous variance result (with a short crossfade), keeping unchanged regions stable and closer to user expectation. The option is exposed in Preferences and is only enabled/usable when DiffSinger Tensor Cache is enabled.

Changes:

• Added a new preference/UI toggle: DiffSingerVarianceLocalPitchPatch (default false), gated by DiffSingerTensorCache.
• Implemented DiffSingerVariancePatch helper to detect pitch-changed ranges and blend variance outputs locally with crossfades and safe fallback behavior.
• Integrated patch-state caching and merge application into DsVariance.Process, plus added unit tests and InternalsVisibleTo for test access.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
OpenUtau.Core/DiffSinger/DiffSingerVariance.cs	Computes a patch key (excluding pitch), caches previous state per phrase, and conditionally applies local merge after variance inference.
OpenUtau.Core/DiffSinger/DiffSingerVariancePatch.cs	New internal helper implementing pitch-diff range detection, weight building, blending, cloning, and metadata-compatibility fallback.
OpenUtau.Core/Util/Preferences.cs	Adds DiffSingerVarianceLocalPitchPatch preference with default false.
OpenUtau/ViewModels/PreferencesViewModel.cs	Binds the new preference into the VM and persists it on change.
OpenUtau/Views/PreferencesDialog.axaml	Adds the new toggle to the DiffSinger section; disables it when tensor cache is off.
OpenUtau/Strings/Strings.axaml	Adds the English resource string for the new toggle label.
OpenUtau.Core/Properties/AssemblyInfo.cs	Adds InternalsVisibleTo("OpenUtau.Test") to allow unit tests to access internal patch helpers.
OpenUtau.Test/Core/DiffSinger/DiffSingerVariancePatchTest.cs	New tests for changed-range grouping, unchanged-pitch preservation, blending behavior, and metadata mismatch fallback.

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[KakaruHayate]

[KakaruHayate]

错误提交，已回滚

[KakaruHayate]

English description:

DiffSinger variance local pitch patch

When users edit pitch, the DiffSinger variance model re-generates the full variance output (energy, breathiness, voicing, tension). Because variance prediction has inherent randomness or global coupling, unedited pitch regions can also shift, deviating from user expectations.

This PR adds an opt-in option (`DiffSingerVarianceLocalPitchPatch = false` by default) that blends only the changed pitch regions' new variance output into the previous result, leaving unchanged regions intact.

How it works

• DiffSingerVariancePatch compares previous and current pitch arrays to find changed frame ranges via `FindChangedRanges`.
• The variance model still runs fully — ONNX inputs are unchanged, so cache remains effective.
• At post-processing, only frames near the changed pitch ranges are replaced in the output; boundary frames use short crossfades (50 ms) to avoid audible seams.
• If no historical state exists, metadata is incompatible, or merge fails for any reason, falls back to the full variance result.

Configuration

• New option `DiffSingerVarianceLocalPitchPatch` (default: `false`).
• Depends on `DiffSingerTensorCache` being enabled. The toggle is disabled in the Preferences UI when tensor cache is off, and the patch is never activated at runtime without cache.

Files (8 files, +272 / -13)

• `OpenUtau.Core/DiffSinger/DiffSingerVariancePatch.cs` (new) — find changed pitch ranges, build blend weights, merge variance outputs with crossfade
• `OpenUtau.Core/DiffSinger/DiffSingerVariance.cs` — integrate patch into variance pipeline
• `OpenUtau.Core/Util/Preferences.cs` — add `DiffSingerVarianceLocalPitchPatch`
• `OpenUtau/ViewModels/PreferencesViewModel.cs` — wire up the toggle
• `OpenUtau/Views/PreferencesDialog.axaml` — add toggle UI (disabled when tensor cache is off)
• `OpenUtau/Strings/Strings.axaml` — localized string
• `OpenUtau.Test/Core/DiffSinger/DiffSingerVariancePatchTest.cs` (new) — unit tests
• `OpenUtau.Core/Properties/AssemblyInfo.cs` — expose internals to test project