fix(bearing): 짝 받침은 거더를 따라 처음 만나는 받침 (직선교 후열 오짝 방지)

검토(2026-11-06): 후열이 전열과 같은 거더 선 위에 같은 방위각으로 놓이면(직선교) 거더선 거리가
둘 다 0이라, A1 받침이 더 먼 P1 후열(다음 경간)과 짝을 짓고 모든 받침에 WS04가 떴다.
- 후보(진행 방향, 방위각 ≤ 0.1°, 거더선 ≤ 0.1 m) 중 거더를 따라 가장 가까운 받침을 짝으로 한다
- 그와 0.5 m 이내로 비슷한 거리의 후보가 더 있을 때만 WS04, 그중 거더선에 가까운 것 사용
- 테스트: A1 + A2만(교각 없음) 짝 성립 S −2 %, A1 + P1에서 전열 계산 · 후열 전열 값 가정(WS03),
  직선교 합성 입력에서 전열 ①–⑤와 짝 · WS04 없음

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/bearing-pair.ts

@@ -24,6 +24,8 @@ export interface PairStructure {
 export const PAIR_AZIMUTH_TOL_DEG = 0.1;
 export const PAIR_OFFSET_TOL_M = 0.1;
 export const AZIMUTH_CHECK_SEC = 10;
+/** Two candidates nearer than this along the girder are ambiguous (WS04). Less than the row spacing (block 1.2 m). */
+export const PAIR_ALONG_TOL_M = 0.5;
 
 export type PairWarning = 'WS01' | 'WS04';
 
@@ -51,8 +53,10 @@ const angleDiffDeg = (a: number, b: number) => Math.abs(((a - b + 540) % 360) -
 
 /**
  * Girder pairs between neighbouring structures (Q-SH1, Q-SH4). For each bearing b on structure k the candidates on k + 1 lie
- * ahead along b's azimuth, within 0.1° of its azimuth and 0.1 m of its girder line; the closest to the line is the pair
- * (WS04 when there were two or more). WS01 when either input azimuth is more than 10″ from the pair direction.
+ * ahead along b's azimuth, within 0.1° of its azimuth and 0.1 m of its girder line. The pair is the first one reached along
+ * the girder: on a straight bridge the next span's bearing (후열) lies on the same line further on, so "closest to the line"
+ * alone would be a tie (2026-11-06 review). WS04 when another candidate is within 0.5 m of it along the girder.
+ * WS01 when either input azimuth is more than 10″ from the pair direction.
  */
 export function girderPairs(structures: PairStructure[]): BearingPair[] {
   const pairs: BearingPair[] = [];
@@ -64,9 +68,12 @@ export function girderPairs(structures: PairStructure[]): BearingPair[] {
         const d = { e: c.x - b.x, n: c.y - b.y };
         return { c, along: d.e * u.e + d.n * u.n, offset: Math.abs(d.e * u.n - d.n * u.e), dAz: angleDiffDeg(c.azimuthDeg, b.azimuthDeg), d };
       }).filter((t) => t.along > 0 && t.dAz <= PAIR_AZIMUTH_TOL_DEG && t.offset <= PAIR_OFFSET_TOL_M)
-        .sort((p, q) => p.offset - q.offset);
+        .sort((p, q) => p.along - q.along);
       if (!candidates.length) continue;
-      const best = candidates[0];
+      // The nearest along the girder, and among those about as near (ambiguous, WS04) the one closest to the line.
+      const near = candidates.filter((t) => t.along - candidates[0].along < PAIR_ALONG_TOL_M).sort((p, q) => p.offset - q.offset);
+      const best = near[0];
+      const ambiguous = near.length > 1;
       const distanceM = Math.hypot(best.d.e, best.d.n);
       const directionDeg = (Math.atan2(best.d.e, best.d.n) / DEG + 360) % 360;
       const fromCheckSec = angleDiffDeg(directionDeg, b.azimuthDeg) * 3600;
@@ -74,7 +81,7 @@ export function girderPairs(structures: PairStructure[]): BearingPair[] {
       const slopePct = ((best.c.z - b.z) / distanceM) * 100;
       const warnings: PairWarning[] = [];
       if (fromCheckSec > AZIMUTH_CHECK_SEC || toCheckSec > AZIMUTH_CHECK_SEC) warnings.push('WS01');
-      if (candidates.length > 1) warnings.push('WS04');
+      if (ambiguous) warnings.push('WS04');
       pairs.push({
         from: { structure: here.name, no: b.no }, to: { structure: next.name, no: best.c.no },
         distanceM, offsetM: best.offset, azimuthDiffDeg: best.dAz, directionDeg, fromCheckSec, toCheckSec,