Add specifications for two-times upscale and unified depth plane features

- Introduced the two-times upscale specification detailing requirements for unified output, fixed model presets, arbitrary dimensions, and consistent job behavior.
- Added scenarios for existing models, repeated upscale, and handling of alpha preservation.
- Created the unified depth plane specification outlining geometry modes, stable interface, and asset evaluation.
- Defined scenarios for mode switching, relief and camera preservation, and validation of delivered assets.

openspec/specs/image-tool-ai-availability/spec.md

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+# image-tool-ai-availability Specification
+
+## Purpose
+TBD - created by archiving change gate-cutout-ai-options. Update Purpose after archive.
+## Requirements
+### Requirement: AI setup entry precedes dependent tool settings
+当 AI 环境或所需模型未就绪时，系统 SHALL 在 Cutout、Image Box 和 Image Lasso 的工具设置开头显示 AI 设置按钮，并使用当前 AI 状态对应的设置文案。
+
+#### Scenario: Cutout AI setup entry is first
+- **WHEN** AI 未就绪且用户激活 Cutout 工具
+- **THEN** 工具设置 SHALL 先显示 AI 设置按钮，再显示 `Fit to Foreground`、`Mesh Sampling Spacing` 和 `Generate Normal Map`
+
+#### Scenario: Image region tool AI setup entry is first
+- **WHEN** AI 未就绪且用户激活 Image Box 或 Image Lasso
+- **THEN** 工具设置 SHALL 先显示 AI 设置按钮，再显示 `Fit to Foreground`
+
+#### Scenario: AI setup entry is omitted when ready
+- **WHEN** AI 环境和所需模型均已就绪
+- **THEN** Cutout、Image Box 和 Image Lasso 的工具设置 SHALL 不显示 AI 设置按钮
+
+### Requirement: AI-dependent settings follow AI availability
+系统 SHALL 仅在 AI 环境和所需模型均已就绪时允许启用图像区域工具的 AI 依赖设置。
+
+#### Scenario: Dependent settings are disabled without AI
+- **WHEN** AI 未就绪
+- **THEN** Cutout 的 `Fit to Foreground` 和 `Generate Normal Map` SHALL 不可编辑
+- **THEN** Image Box 和 Image Lasso 的 `Fit to Foreground` SHALL 不可编辑
+- **THEN** Cutout 的 `Mesh Sampling Spacing` SHALL 保持可编辑
+
+#### Scenario: Dependent settings are enabled with AI
+- **WHEN** AI 环境和所需模型均已就绪
+- **THEN** Cutout 的 `Fit to Foreground` 和 `Generate Normal Map` SHALL 可编辑
+- **THEN** Image Box 和 Image Lasso 的 `Fit to Foreground` SHALL 可编辑
+
+### Requirement: Cutout shape choices follow AI availability
+系统 SHALL 根据 AI 可用性限制 Cutout shape pie 中的可选 shape，同时保留四种 shape 的底层实现。
+
+#### Scenario: Two local shapes without AI
+- **WHEN** AI 未就绪且用户完成 Cutout 区域选择
+- **THEN** shape pie SHALL 只显示 `Surface` 和 `Balloon`
+
+#### Scenario: Four shapes with AI
+- **WHEN** AI 环境和所需模型均已就绪且用户完成 Cutout 区域选择
+- **THEN** shape pie SHALL 显示 `Surface`、`Balloon`、`Depth Balloon` 和 `Depth Surface`
+
+#### Scenario: Runtime RNA menu shape assignment
+- **WHEN** a displayed Cutout shape is selected on a Blender version that exposes modifier inputs through runtime RNA
+- **THEN** the system SHALL assign the matching string enum identifier and create the shape successfully
+
+### Requirement: Stale AI settings do not trigger generation
+系统 MUST 在区域交互读取设置时忽略 AI 未就绪状态下遗留为真的 AI 依赖选项。
+
+#### Scenario: Local Cutout remains local with stale settings
+- **WHEN** AI 未就绪、`Fit to Foreground` 或 `Generate Normal Map` 的保存值为真，且用户选择 `Surface` 或 `Balloon`
+- **THEN** Cutout operator SHALL 接收关闭的 AI 依赖选项
+- **THEN** 操作 SHALL 不因这些遗留值启动 AI job 或打开 AI 设置流程
+