Replaces the binary Wireframe/Solid toggle with a 7-mode dropdown
that maps onto acadrust's `ViewportRenderMode` enum: Wireframe 2D /
Wireframe 3D / Hidden Line / Flat Shaded / Gouraud Shaded / Flat
Shaded + Edges / Gouraud Shaded + Edges. Per-tab state lives on
`DocumentTab::render_mode`; the old `SetWireframe` message forwards
to `SetRenderMode` so the ribbon + WIREFRAME / SOLID command line
keep working.
`scene::render::render_mode_flags()` translates the mode into three
pipeline-facing booleans (`face3d_fill`, `mesh_fill`,
`show_3d_edges`); `mesh_fill` / `show_3d_edges` are stubs that the
upcoming phases will consume. `Primitive` carries the derived
`view_wireframe` plus the two new fields through to `prepare()`.
`Pipeline::upload_face3d` takes a `wireframe_only` flag that drops
3DFACE quad fills (built from `key_vertices`) while keeping the
`all_wires.fill_tris` channel — that channel carries text-LOD greek
rectangles and PolyfaceMesh face triangles which must stay visible
in wireframe mode. 3DFACE edges stay on regardless of mode.
Solid3D mesh wireframe rendering, Hidden Line z-prepass, and Flat /
Gouraud shader uniforms come in phases 1–4.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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