Add renderer depth state contract

docs/modernization/roadmap.md

@@ -419,9 +419,9 @@ context, render device, shader program descriptor, mesh, render target,
 readback byte-size helpers, texture-upload/readback command validation,
 frame-capture byte-size helpers, frame-capture command validation,
 render-target blit validation, texture-slot binding validation, blend-state
-validation, scissor-state validation, trace interface validation, and the
-canonical PanoPainter shader catalog now consumed by the legacy OpenGL app
-initialization path.
+validation, scissor-state validation, depth-state validation, trace interface
+validation, and the canonical PanoPainter shader catalog now consumed by the
+legacy OpenGL app initialization path.
 `pp_renderer_gl` now exists as the first OpenGL backend library and owns pure
 OpenGL capability detection for framebuffer fetch, map-buffer alignment, and
 float texture support. It also owns the OpenGL texture upload-type mapping used
@@ -724,7 +724,7 @@ Results:
   validation, texture-upload byte-count validation, frame-capture byte-size and
   command-order validation, render-target blit validation, texture-slot binding
   validation, blend-state validation, scissor-state validation, recording
-  scissor/blend/texture-bind/upload/readback/frame-capture/blit command
+  scissor/depth/blend/texture-bind/upload/readback/frame-capture/blit command
   capture, and invalid catalog rejection.
 - `pp_paint_renderer_compositor_tests` passed.
 - `pp_ui_core_color_tests` passed.
@@ -819,16 +819,16 @@ Results:
   reintroduces raw `GL_*`/`WGL_*` constants outside the allowed legacy OpenGL
   implementation files.
 - `pp_renderer_api` now includes a headless `RecordingRenderDevice` with strict
-  command-order/scissor-state/blend-state/texture-bind/texture-upload/readback/
-  frame-capture/blit validation; it records commands, trace markers, scissor
-  state, blend state, texture binds, uploads/readbacks, frame captures, and
-  render-target blits, giving automation a backend-neutral render path that
-  does not require a window or GL context.
+  command-order/scissor-state/depth-state/blend-state/texture-bind/
+  texture-upload/readback/frame-capture/blit validation; it records commands,
+  trace markers, scissor state, depth state, blend state, texture binds,
+  uploads/readbacks, frame captures, and render-target blits, giving automation
+  a backend-neutral render path that does not require a window or GL context.
 - `pano_cli record-render` exercises that headless recording renderer and emits
   JSON command counts, target dimensions, backend name, trace/draw summary, and
-  scissor/blend-state plus texture-bind/upload/readback/frame-capture/blit
-  command/byte totals for agent automation, with an expected-failure smoke for
-  oversized render/readback targets.
+  scissor/depth/blend-state plus texture-bind/upload/readback/frame-capture/
+  blit command/byte totals for agent automation, with an expected-failure smoke
+  for oversized render/readback targets.
 - `pano_cli simulate-document-history` exercises pure document history
   apply/undo/redo behavior and emits JSON layer/frame/history state for agent
   automation.