refactor(b06): 횡단 카드 렌더러 기능별 나눔 — 조정창 두 벌 · 지반선 · 팬 범위 분리(137-1)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018jonfdxn1Xit9bdkNJpE4G

B06_Section/B06_Section_UI_Cross_View_Frame.ts

@@ -6,7 +6,7 @@
 
 import type { CrossSection } from "./B06_Section_Api_Fetch";
 import { computeStructureAreas, type DesignTrim } from "@util/common_util_cross_structure_areas";
-import { CROSS_PAD, L, svgElement, svgText } from "./B06_Section_UI_Section_Common";
+import { CROSS_PAD, L, svgElement, svgText, validElevation } from "./B06_Section_UI_Section_Common";
 
 type Sample = CrossSection["samples"][number];
 
@@ -124,3 +124,43 @@ export function applyStructureAreas(
     design.cut_soil_area_m2 = Number(areas.cutSoilAreaM2.toFixed(4));
   }
 }
+
+/** 원지반선 — 끊긴 샘플(무효 표고)마다 폴리선을 나눠 그린다. `toY` = 표고 → 화면 y(배율 반영). */
+export function appendGroundProfile(
+  plotLayer: SVGElement,
+  samples: Sample[],
+  x: (offset: number) => number,
+  toY: (elevation: number) => number,
+): void {
+  const segments: string[] = [];
+  let current: string[] = [];
+  for (const sample of samples) {
+    if (!validElevation(sample)) {
+      if (current.length > 1) segments.push(current.join(" "));
+      current = [];
+      continue;
+    }
+    current.push(`${x(sample.offset_m ?? 0)},${toY(sample.elevation_m)}`);
+  }
+  if (current.length > 1) segments.push(current.join(" "));
+  segments.forEach((points) =>
+    plotLayer.append(svgElement("polyline", { points, class: "b06-chart__cross-profile" })),
+  );
+}
+
+/** 팬 한계로 쓸 **그려진 범위** — 캐시 전 구간의 좌우 끝과 표고 상 · 하단(없으면 undefined). */
+export function drawnContentBounds(
+  samples: Sample[],
+  x: (offset: number) => number,
+  toY: (elevation: number) => number,
+): { x: number; width: number; y: number; height: number } | undefined {
+  const offsets = samples.map((sample) => sample.offset_m ?? 0);
+  const displayY = samples.filter(validElevation).map((sample) => toY(sample.elevation_m));
+  if (!offsets.length || !displayY.length) return undefined;
+  return {
+    x: x(Math.max(...offsets)),
+    width: x(Math.min(...offsets)) - x(Math.max(...offsets)),
+    y: Math.min(...displayY),
+    height: Math.max(...displayY) - Math.min(...displayY),
+  };
+}