cimery Sprint 1 — Rust 워크스페이스 + 전 계층 파이프라인

8개 크레이트 구현, cargo test 32개 전부 통과:
- core: Mm/M 단위 newtype, UnitExt 리터럴, FeatureError
- ir: GirderIR + 전 단면 파라미터(PSC-I/U/SteelBox/PlateI) serde JSON
- dsl: Girder builder + 검증 (경간 범위·count·spacing)
- kernel: GeomKernel trait + StubKernel (box mesh, AABB)
- incremental: dirty-tracking IncrementalDb (salsa 업그레이드 경로 주석)
- evaluator: 상태 없는 IR→kernel 브리지
- usd: USDA 1.0 텍스트 익스포트 (CimeryBridgeAPI·GirderAPI schema)
- viewer: wgpu 22 + winit 0.30 컬러 삼각형 (Sprint 1 proof-of-concept)

Sprint 2 다음 단계:
- opencascade-rs로 StubKernel 교체 (실제 PSC-I sweep)
- viewer에서 Girder Mesh 렌더 + 카메라 orbit

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

cimery/crates/usd/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name    = "cimery-usd"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+cimery-ir  = { workspace = true }
+
+[dev-dependencies]
+cimery-core = { workspace = true }

cimery/crates/usd/src/lib.rs

@@ -0,0 +1,151 @@
+//! cimery-usd — USDA 1.0 text export.
+//!
+//! Sprint 1: stub geometry (box) — real B-rep export follows in Sprint 2
+//! after `GeomKernel` backends produce STEP/BREP that can be tessellated.
+//!
+//! ADR-002 O / ADR-003 A4:
+//! - USD is the *output format*, not a DSL.
+//! - All cimery-specific concepts are captured as Applied API schemas
+//!   (`CimeryBridgeAPI`, `CimeryGirderAPI`) using the codeless USD schema approach.
+//! - IFC alias double-tagging planned for Sprint 3 (AOUSD AECO spec alignment).
+
+use cimery_ir::GirderIR;
+
+// ─── Single girder export ─────────────────────────────────────────────────────
+
+/// Export one [`GirderIR`] to a self-contained USDA 1.0 string.
+///
+/// Sprint 1: stub box geometry (600 × 1800 × span_mm).
+/// The real geometry path is: IR → Evaluator → Mesh → USD Mesh prim.
+pub fn girder_to_usda(ir: &GirderIR) -> String {
+    let id_str = safe_id(ir);
+    let pts    = box_points(ir.span_mm() as f32);
+
+    let mut s = String::with_capacity(1024);
+    s.push_str(USDA_HEADER);
+    s.push_str("def Xform \"Bridge\" (\n");
+    s.push_str("    apiSchemas = [\"CimeryBridgeAPI\"]\n");
+    s.push_str(")\n{\n");
+    write_girder_prim(&mut s, ir, &id_str, &pts);
+    s.push_str("}\n");
+    s
+}
+
+/// Export multiple girders to a single USDA file under one Bridge prim.
+pub fn girders_to_usda(girders: &[GirderIR]) -> String {
+    let mut s = String::with_capacity(girders.len() * 512 + 256);
+    s.push_str(USDA_HEADER);
+    s.push_str("def Xform \"Bridge\" (\n");
+    s.push_str("    apiSchemas = [\"CimeryBridgeAPI\"]\n");
+    s.push_str(")\n{\n");
+    for ir in girders {
+        let id_str = safe_id(ir);
+        let pts    = box_points(ir.span_mm() as f32);
+        write_girder_prim(&mut s, ir, &id_str, &pts);
+    }
+    s.push_str("}\n");
+    s
+}
+
+// ─── Helpers ──────────────────────────────────────────────────────────────────
+
+fn safe_id(ir: &GirderIR) -> String {
+    ir.id.to_string().replace('-', "_")
+}
+
+fn box_points(span: f32) -> String {
+    format!(
+        "(0 0 0) (600 0 0) (600 1800 0) (0 1800 0) \
+         (0 0 {s}) (600 0 {s}) (600 1800 {s}) (0 1800 {s})",
+        s = span,
+    )
+}
+
+const USDA_HEADER: &str =
+    "#usda 1.0\n(\n    metersPerUnit = 0.001\n    upAxis = \"Y\"\n)\n\n";
+
+fn write_girder_prim(s: &mut String, ir: &GirderIR, id_str: &str, pts: &str) {
+    s.push_str(&format!("    def Xform \"Girder_{}\" (\n", id_str));
+    s.push_str("        apiSchemas = [\"CimeryGirderAPI\"]\n");
+    s.push_str("    ) {\n");
+    s.push_str(&format!(
+        "        custom float cimery:stationStart = {}\n", ir.station_start
+    ));
+    s.push_str(&format!(
+        "        custom float cimery:stationEnd = {}\n", ir.station_end
+    ));
+    s.push_str(&format!("        custom int cimery:count = {}\n", ir.count));
+    s.push_str(&format!(
+        "        custom token cimery:sectionType = \"{:?}\"\n", ir.section_type
+    ));
+    s.push_str(&format!(
+        "        custom token cimery:material = \"{:?}\"\n", ir.material
+    ));
+    s.push('\n');
+    s.push_str("        def Mesh \"geometry\" {\n");
+    s.push_str(
+        "            int[] faceVertexCounts = \
+         [3 3 3 3 3 3 3 3 3 3 3 3]\n"
+    );
+    s.push_str(
+        "            int[] faceVertexIndices = \
+         [0 2 1 0 3 2 4 5 6 4 6 7 0 4 7 0 7 3 1 2 6 1 6 5 0 1 5 0 5 4 3 7 6 3 6 2]\n"
+    );
+    s.push_str(&format!(
+        "            point3f[] points = [{}]\n", pts
+    ));
+    s.push_str("        }\n");
+    s.push_str("    }\n");
+}
+
+// ─── Tests ────────────────────────────────────────────────────────────────────
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use cimery_core::{MaterialGrade, SectionType};
+    use cimery_ir::{FeatureId, GirderIR, PscISectionParams, SectionParams};
+
+    fn sample() -> GirderIR {
+        GirderIR {
+            id:                    FeatureId::new(),
+            station_start:         100.0,
+            station_end:           140.0,
+            offset_from_alignment: 0.0,
+            section_type:          SectionType::PscI,
+            section: SectionParams::PscI(PscISectionParams::kds_standard()),
+            count:    5,
+            spacing:  2500.0,
+            material: MaterialGrade::C50,
+        }
+    }
+
+    #[test]
+    fn usda_header_present() {
+        let s = girder_to_usda(&sample());
+        assert!(s.starts_with("#usda 1.0"), "must start with USDA header");
+    }
+
+    #[test]
+    fn contains_bridge_api() {
+        let s = girder_to_usda(&sample());
+        assert!(s.contains("CimeryBridgeAPI"));
+        assert!(s.contains("CimeryGirderAPI"));
+    }
+
+    #[test]
+    fn contains_station_values() {
+        let s = girder_to_usda(&sample());
+        assert!(s.contains("100"), "should contain station_start");
+        assert!(s.contains("140"), "should contain station_end");
+    }
+
+    #[test]
+    fn multiple_girders() {
+        let girders = vec![sample(), sample()];
+        let s = girders_to_usda(&girders);
+        assert!(s.contains("CimeryBridgeAPI"));
+        // Two distinct prim blocks
+        assert_eq!(s.matches("CimeryGirderAPI").count(), 2);
+    }
+}