Sprint 14~22 — egui 리본 UI + OcctKernel B-rep + 가로보/신축이음 + 선형 좌표 + USD 익스포트 + WASM + CI/CD + 테스트 4층

Sprint 14: egui TopBottomPanel 리본 + CollapsingHeader SidePanel (상부구조·추가부재·선형·프로젝트)
Sprint 15: IncrementalDb 전 Feature 타입 확장 (girder→7종), dirty-tracking 20 unit tests
Sprint 16: Gitea + GitHub Actions CI/CD (check/test/clippy/fmt + 멀티플랫폼 릴리스)
Sprint 17: AlignmentTransform + AlignmentScene — 선형 국소 프레임 → 세계 좌표 변환
Sprint 18: OcctKernel 교각(16각형 기둥+코핑) + 교대(흉벽+푸팅+날개벽) B-rep
Sprint 19: CrossBeamIR + ExpansionJointIR — IR/DSL/kernel/scene 전 계층, sweep_profile_flat_x
Sprint 20: 테스트 4층 — Layer1 insta 스냅샷(7종), Layer2 기하 불변량(19), Layer3 두-커널(7), Layer4 proptest(7) — 61 tests pass
Sprint 21: cimery-usd PureRustKernel 실제 기하 변환 + BridgeExporter 증분 캐시
Sprint 22: viewer wasm feature + wasm-bindgen/web-sys + GitHub Actions Cloudflare Pages 배포

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cimery/crates/ir/src/lib.rs

@@ -321,6 +321,62 @@ pub struct AbutmentIR {
     pub material:                cimery_core::MaterialGrade,
 }
 
+// ─── Cross Beam IR ────────────────────────────────────────────────────────────
+
+/// Fully-resolved Cross Beam (가로보) specification. Sprint 19.
+///
+/// Cross beams provide lateral bracing between girders at regular intervals.
+/// All dimensions in mm; station in m.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct CrossBeamIR {
+    pub id:              FeatureId,
+    /// Station along alignment [m] — position of this cross beam set.
+    pub station:         f64,
+    pub section:         cimery_core::CrossBeamSection,
+    /// Web height (distance between flange centrelines) [mm].
+    pub web_height:      f64,
+    /// Web plate thickness [mm].
+    pub web_thickness:   f64,
+    /// Flange width [mm].
+    pub flange_width:    f64,
+    /// Flange thickness [mm].
+    pub flange_thickness:f64,
+    /// Number of girder bays to span (= girder_count - 1).
+    pub bay_count:       u32,
+    /// Girder c/c spacing [mm] — defines beam length per bay.
+    pub girder_spacing:  f64,
+    pub material:        cimery_core::MaterialGrade,
+}
+
+impl CrossBeamIR {
+    /// Total length of one cross beam [mm].
+    pub fn total_length_mm(&self) -> f64 {
+        self.bay_count as f64 * self.girder_spacing
+    }
+}
+
+// ─── Expansion Joint IR ───────────────────────────────────────────────────────
+
+/// Fully-resolved Expansion Joint (신축이음) specification. Sprint 19.
+///
+/// Placed at the ends of a span or at pier locations to allow relative movement.
+/// All dimensions in mm; station in m.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct ExpansionJointIR {
+    pub id:            FeatureId,
+    /// Station along alignment [m].
+    pub station:       f64,
+    pub joint_type:    cimery_core::ExpansionJointType,
+    /// Opening gap width [mm] — clear distance at nominal position.
+    pub gap_width:     f64,
+    /// Total transverse width [mm] — same as deck width.
+    pub total_width:   f64,
+    /// Total assembly depth [mm].
+    pub depth:         f64,
+    /// Design movement range [mm] — max expansion/contraction.
+    pub movement_range:f64,
+}
+
 // ─── Tests ────────────────────────────────────────────────────────────────────
 
 #[cfg(test)]