ModelCraft foundation: workspace, quality gates, FE model, command engine, geometry boundary

A pure-Rust CAE modeling workspace following the SolidCraft conventions:
- modelcraft-model: nodes and elements by label with hostile-input validation
- modelcraft-geometry: SolidCraft's kernel (pinned git dependency) behind our own API;
  tessellation into a face-tagged boundary surface for volume meshing
- modelcraft-engine: CommandSpec registry, Session::execute with rollback and panic guard,
  scripts and a journal
- modelcraft-cli: list commands, run scripts
- xtask: layers (only geometry may use solidcraft-*), assets, licences, tests, wasm, ci
- AGENTS.md, architecture, ADR 0001 (libraries and licences), roadmap, CI

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

ATTRIBUTION.md

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+# Attribution
+
+Every non-code asset in this repository (images, icons, fonts, example geometry) is listed here
+with its author, source and licence. `cargo xtask assets` (part of `cargo xtask ci`) fails if an
+asset file is missing from this table.
+
+**Policy (mandatory):** ModelCraft contains **no iconography, images, artwork, fonts, templates,
+example decks or help text from commercial CAE products.** Every asset is original work by
+ModelCraft contributors or third-party material under an open licence. Screenshots of commercial
+software are never committed.
+
+## Files
+
+| File | Author | Source | Licence |
+|---|---|---|---|
+
+## Adapted code
+
+| File | Adapted from | Licence |
+|---|---|---|
+| xtask/src/layers.rs | SolidCraft `xtask/src/layers.rs` (itself adapted from CADCraft's xtask) | MIT OR Apache-2.0 |
+| xtask/src/assets.rs, xtask/src/licences.rs, xtask/src/test.rs, xtask/src/main.rs | SolidCraft `xtask/src/` | MIT OR Apache-2.0 |
+| clippy.toml, rustfmt.toml | SolidCraft | MIT OR Apache-2.0 |