Add renderer mipmap command contract

docs/modernization/roadmap.md

@@ -417,12 +417,13 @@ Status: started. `pp_renderer_api` exists as a headless renderer-neutral target
 with explicit texture usage flags, texture descriptor, byte-size, viewport,
 mesh, readback bounds, command context, render device, shader program
 descriptor, mesh, render target, readback byte-size helpers,
-texture-upload/readback command validation, frame-capture byte-size helpers,
+texture mip-level validation, texture-upload/readback command validation,
+mipmap-generation 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,
 depth-state validation, trace interface validation, sampler-state validation,
-and the canonical PanoPainter shader catalog now consumed by the legacy
-OpenGL app initialization path.
+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
@@ -722,7 +723,8 @@ Results:
   plus malformed payload rejection at the export boundary.
 - `pp_renderer_api_tests` passed, including shader descriptor validation,
   PanoPainter shader catalog validation, explicit texture usage validation,
-  readback byte-size and command-order validation, texture-upload byte-count
+  texture mip-level validation, readback byte-size and command-order
+  validation, texture-upload byte-count validation, mipmap-generation command
   validation, frame-capture byte-size and command-order validation,
   render-target blit validation, texture-slot binding validation, blend-state
   validation, scissor-state validation, render-pass color/depth/stencil clear
@@ -829,15 +831,15 @@ Results:
   renderer-owned resource factory and
   command-order/render-pass-clear/scissor-state/depth-state/blend-state/
   texture-usage/texture-bind/sampler-bind/shader-uniform/texture-upload/
-  readback/frame-capture/blit validation plus explicit draw descriptor and
-  texture-copy validation; it creates validated textures, render targets,
-  shaders, meshes, and readback buffers, then records commands, trace markers,
-  render-pass
+  mipmap-generation/readback/frame-capture/blit validation plus explicit draw
+  descriptor and texture-copy validation; it creates validated textures,
+  render targets, shaders, meshes, and readback buffers, then records commands,
+  trace markers, render-pass
   color/depth/stencil clear intent, scissor state, depth state, blend state,
   shader uniform writes, texture/sampler binds, draw mesh inputs, explicit draw
-  ranges, texture uploads/copies/readbacks, frame captures, and render-target
-  blits, giving automation a backend-neutral render path that does not require
-  a window or GL context.
+  ranges, texture uploads/mipmap generations/copies/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, resource creation counts, target dimensions, backend
   name, trace/draw summary, render-pass/depth-clear counts, and draw