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/ai-operator-failure-handling/spec.md

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+# ai-operator-failure-handling Specification
+
+## Purpose
+TBD - created by archiving change unify-ai-input-validation. Update Purpose after archive.
+## Requirements
+### Requirement: Expected operator failures are reported normally
+
+AI 操作 SHALL 将输入准备与嵌套 Operator 调用的预期失败转换为普通错误提示和 CANCELLED，包括 Remove BG、Depth/Relief Plane、AI Environment 准备及现有 Panorama 入口。提示 SHALL 保留原因并避免重复的 Blender 错误前缀。
+
+#### Scenario: Nested input validation failure
+- **WHEN** 内部 Job Operator 报告无效输入且 bpy.ops 抛出 RuntimeError
+- **THEN** 外部入口返回 CANCELLED，显示原因，不向用户展示未捕获的 Python traceback
+
+#### Scenario: Environment setup failure
+- **WHEN** AI Environment 设置入口调用安装或下载 Operator 同步失败
+- **THEN** 设置入口及调用它的 AI 操作按普通错误取消
+
+#### Scenario: Successful job startup
+- **WHEN** 内部 Job Operator 返回 RUNNING_MODAL
+- **THEN** 外部入口保持现有成功返回与异步处理语义，源图片及 Undo 行为保持有效
+
+### Requirement: Temporary inputs have explicit ownership
+
+系统 SHALL 释放本次操作创建的临时输入，在准备失败、启动失败、取消及异步结束时均有负责清理的边界；用户原文件 SHALL 保持不变。
+
+#### Scenario: Preparation failure
+- **WHEN** packed 图片导出或序列复制失败
+- **THEN** 准备函数删除本次临时文件和目录，并保留源图片与源文件
+
+#### Scenario: Synchronous nested failure
+- **WHEN** 临时输入准备成功后内部 Operator 抛错或返回 CANCELLED
+- **THEN** 临时输入被清理，外部操作取消，源图片引用保持不变
+
+#### Scenario: Asynchronous completion
+- **WHEN** Job 接管临时输入并在之后成功、失败或取消
+- **THEN** 输入在 Job 结束时清理，运行期间保持可用，用户原文件不被删除
+