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/cutout-attribute-lifecycle/spec.md

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+# cutout-attribute-lifecycle Specification
+
+## Purpose
+TBD - created by archiving change optimize-cutout-geometry-nodes. Update Purpose after archive.
+## Requirements
+### Requirement: Internal Cutout attributes use the `_o_` prefix
+
+Attributes that exist only inside the Cutout geometry node lifecycle and are removed before output SHALL use the `_o_` prefix. The system SHALL NOT use the previous `.o_anyimage_*` prefix for new internal attributes.
+
+#### Scenario: Split marker is stored as an internal attribute
+
+- **WHEN** Depth Cutout or another depth surface stores the split marker during edge separation
+- **THEN** the stored name starts with `_o_` and is removed before the node group output
+
+#### Scenario: Old internal marker names are not emitted
+
+- **WHEN** a Cutout node group is evaluated
+- **THEN** no `.o_anyimage_depth_cut` or `.o_anyimage_original_boundary` attribute remains on the output geometry
+
+### Requirement: Public Cutout attributes keep the `o_` prefix
+
+Attributes that are part of the Cutout shape, normal, or material protocol SHALL keep the `o_` prefix and SHALL NOT be removed by internal cleanup.
+
+#### Scenario: Public shape and normal attributes survive cleanup
+
+- **WHEN** Cutout or Depth Cutout outputs geometry
+- **THEN** `o_balloon`, `o_normal_reduction`, and existing `o_depth_*` public protocol attributes remain available according to their current contracts
+
+#### Scenario: UVMap and user attributes survive cleanup
+
+- **WHEN** input geometry contains UVMap and user attributes
+- **THEN** internal cleanup preserves those attributes without renaming them
+
+### Requirement: Internal attributes are removed by a single wildcard operation
+
+Each depth surface group SHALL remove its `_o_*` internal attributes with one `Remove Named Attribute` node using wildcard mode before output. It SHALL NOT remove internal attributes one by one.
+
+#### Scenario: Wildcard cleanup removes all internal attributes
+
+- **WHEN** a depth surface group evaluates with Split or Thickness enabled
+- **THEN** every `_o_*` attribute is absent from the output geometry
+
+#### Scenario: Wildcard cleanup is safe when no internal attribute exists
+
+- **WHEN** a depth surface group evaluates with the corresponding internal path disabled
+- **THEN** the wildcard removal produces no missing-attribute warning and leaves public attributes unchanged
+