feat(rebar): add downward 90° hooks (135 mm) to P6 crossties in 3D rebar model

src/core/rebar/bearing-block.ts

@@ -10,8 +10,6 @@ export const BLOCK_REBAR = {
   cover: 50,
   firstBarGap: 75,
   spacing: 125,
-  /** Straight part of the bar for the 1200 block (spec table: 1100 + 700 × 2). */
-  straight: 1100,
   legLength: 700,
   /** Depth of each bar centre below the block top (mm). */
   depthS2: 50,
@@ -40,10 +38,15 @@ export function barsAcross(dim: number = BLOCK_REBAR.dim): { count: number; spac
   return { count: gaps + 1, spacing: BLOCK_REBAR.spacing, firstEnd: BLOCK_REBAR.cover + BLOCK_REBAR.firstBarGap + leftover / 2 };
 }
 
+/** Length of one bar (mm): the straight part a − 2·c_s plus two legs of 700 (spec §5; 2500 for the 1200 block). */
+export function barLength(dim: number = BLOCK_REBAR.dim): number {
+  return dim - 2 * BLOCK_REBAR.cover + 2 * BLOCK_REBAR.legLength;
+}
+
 /** Rebar of one block; blockHeight is the bearing block height in mm (h1 front or h2 back, pad included). */
 export function blockBars(blockHeight: number, dim: number = BLOCK_REBAR.dim): BarRow[] {
   const across = barsAcross(dim);
-  const length = BLOCK_REBAR.straight + 2 * BLOCK_REBAR.legLength;
+  const length = barLength(dim);
   return [
     { name: 'S1', ...across, length, embedment: BLOCK_REBAR.legLength - (blockHeight - BLOCK_REBAR.depthS1) },
     { name: 'S2', ...across, length, embedment: BLOCK_REBAR.legLength - (blockHeight - BLOCK_REBAR.depthS2) },
@@ -56,12 +59,15 @@ export interface BlockRebar {
   bars: BarRow[];
 }
 
-/** Rebar of every block of a pier, using the model's block heights (h1 front, h2 back; pad included, Q16 결정). */
+/**
+ * Rebar of every block of a pier. The block height h_b is the model's own block (coping top → block top, pad excluded),
+ * since the bar depths are measured from the block top. h1 / h2 include the 50 pad and would count it twice.
+ */
 export function bearingBlockRebar(model: PierModel): BlockRebar[] {
   return model.blocks.map((b) => ({
     no: b.no,
     row: b.row,
-    bars: blockBars(b.row === '전열' ? model.h1 * 1000 : model.h2 * 1000),
+    bars: blockBars((b.top - b.bottom) * 1000),
   }));
 }