Desktop app: egui/wgpu viewport, model tree, commands and control channel (#9)

* render: display data from the FE model, orbit camera and CPU rasterizer

modelcraft-render (L1, no GPU): DisplayMesh (the unshared faces of solid
elements, shells, element edges, line elements, nodes), the orbit camera
and a CPU rasterizer with PNG output for headless snapshots, adapted from
SolidCraft's render crate. Workspace: egui/eframe/egui-wgpu 0.36 and
SolidCraft's patched egui-wgpu from the pinned rev.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* engine: sample model script (a hex8 block and a tet4 cube)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* Desktop app: egui/wgpu viewport, model tree, commands, status bar, control channel

modelcraft-ui-egui (L5): ModelApp over the engine Session; GPU viewport
(lit faces, element edges, nodes) with a CPU fallback; orbit/pan/zoom,
standard views and fit; model tree; commands panel generated from the
registry with a JSON parameter form; status bar; control request
handling (engine.*, ui.*, ui.screenshot, ui.render). apps/modelcraft:
eframe window, --sample, --control PORT loopback JSON-lines server.
Adapted from SolidCraft's ui-egui and app.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* THIRD-PARTY-LICENSES: the desktop app's dependencies

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* docs: control protocol, desktop app in architecture, roadmap and attribution

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* render: simplify the display mesh (sorted face keys over maps, no unused fields)

Interior faces are found by sorting fixed-size face keys instead of a BTreeMap of Vecs, edges
are deduplicated by sort, and each element's corners are looked up once. Drops the unused
`element` fields on DisplayTri/DisplayLine, the unused Mat4::IDENTITY and corner_count, and
hoists the line colour out of the raster loop.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

* viewport: split GPU geometry into batches within the buffer limit; refuse oversized CPU renders

A mesh with a few million boundary triangles made one vertex buffer larger than the device's
max_buffer_size (256 MiB under the limits eframe requests), and wgpu's default error handler
panicked. Geometry is now uploaded in batches of whole primitives, each at most 128 MiB and the
device limit, and all are drawn. A device error handler logs errors and shows them in the status
bar instead of panicking.

The CPU renderer refuses sizes over 8192 per side or 16 MP, and scenes over 20 million
primitives, with an error, and allocates its buffers fallibly. ui.render reports a size out of
range instead of clamping it; the CPU viewport fits a large window into the limit.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NmAttHhUZTokgPeEJia8sm

---------

Co-authored-by: jyviko <2501648+jyviko@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

docs/architecture.md

@@ -23,19 +23,21 @@ crates in strictly lower layers.
 | L1 | `modelcraft-mesh` | Surface preparation (weld, watertightness, feature edges), robust predicates, Delaunay tetrahedralization and refinement, Voronoi-based optimization, hex meshing, quality metrics. | started |
 | L1 | `modelcraft-solver` | Element formulations, assembly, sparse linear static and modal solution. | planned |
 | L1 | `modelcraft-decks` | Abaqus input, Nastran bulk data and LS-DYNA keyword readers and writers, to and from `model`. | planned |
-| L1 | `modelcraft-render` | Display data (meshes, contour maps) without a GPU dependency. | planned |
+| L1 | `modelcraft-render` | Display data without a GPU dependency: the visible faces, element edges and nodes of a model, the orbit camera, a CPU rasterizer for headless snapshots; contour maps later. | started |
 | L2 | `modelcraft-doc` | The document: geometry, mesh, model, results, history. | planned |
 | L3 | `modelcraft-io` | `.modelcraft` files, result files. | planned |
 | L4 | `modelcraft-engine` | Commands (`CommandSpec`), `Session::execute` with rollback and the panic guard, scripts. | started |
-| L5 | `modelcraft-ui-egui`, `modelcraft-mcp` | Desktop UI, control channel and MCP server. | planned |
+| L5 | `modelcraft-ui-egui`, `modelcraft-mcp` | Desktop UI (egui + wgpu viewport, model tree, commands, status bar) and control channel requests (docs/control-protocol.md); MCP server. | ui started |
 | testkit | `modelcraft-testkit` | Test tooling, a dev-dependency only: the meshing test corpus (`tests/corpus/*/recipe.json`, analytic shapes) and its runner (`cargo xtask corpus`). | started |
-| apps | `modelcraft`, `modelcraft-cli`, `modelcraft-web` | Desktop, command line, browser. | cli started |
+| apps | `modelcraft`, `modelcraft-cli`, `modelcraft-web` | Desktop, command line, browser. | desktop, cli started |
 
 Rules beyond the layer order:
 - Nothing below L5 uses egui, eframe, winit, wgpu or rfd.
 - Only `modelcraft-geometry` uses `solidcraft-*`, pinned by rev in the workspace `Cargo.toml`.
   SolidCraft's `[patch.crates-io]` (its fixed truck crates) does not reach dependents, so the
-  workspace repeats it from the same rev; bump both together.
+  workspace repeats it from the same rev; bump both together. The same goes for SolidCraft's
+  patched `egui-wgpu` (MSAA clamped to what the device supports, 1x on OpenGL adapters, so the
+  desktop app's 4x never fails pipeline validation at start).
 - Everything below the apps builds for `wasm32-unknown-unknown`.
 - `modelcraft-geometry`'s non-default `scripts` feature builds designs from SolidCraft command
   scripts (`script_design`, through `solidcraft-engine`) for the test corpus; the library opens