Fix label placement for curved and spur symbols

- Curved: position text at arc band midpoint, rotated along the curve
- Spur: center text in the trapezoid shape, not the bounding box

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

svelte-app/src/lib/canvas/renderer.ts

@@ -546,28 +546,39 @@ function parseConveyanceLabel(label: string): { lines: string[]; stripped: strin
 /** Draw label inside a conveyance symbol — black bold text, auto-sized to fit */
 function drawConveyanceLabel(ctx: CanvasRenderingContext2D, sym: PlacedSymbol) {
   if (!sym.label) return;
+
+  if (isCurvedType(sym.symbolId)) { drawCurvedLabel(ctx, sym); return; }
+
   const { lines, stripped } = parseConveyanceLabel(sym.label);
   const pad = 2;
-  const availW = sym.w - pad * 2;
+
-  const availH = sym.h - pad * 2;
+  // For spurs, center in the trapezoid shape, not bounding box
-  const cx = sym.x + sym.w / 2;
+  let cx: number, cy: number, availW: number, availH: number;
-  const cy = sym.y + sym.h / 2;
+  if (isSpurType(sym.symbolId)) {
+    const w2 = sym.w2 ?? sym.w;
+    const midW = (w2 + sym.w) / 2; // width at vertical midpoint
+    cx = sym.x + midW / 2;
+    cy = sym.y + sym.h / 2;
+    availW = midW - pad * 2;
+    availH = sym.h - pad * 2;
+  } else {
+    cx = sym.x + sym.w / 2;
+    cy = sym.y + sym.h / 2;
+    availW = sym.w - pad * 2;
+    availH = sym.h - pad * 2;
+  }
 
   ctx.fillStyle = '#000000';
   ctx.textAlign = 'center';
   ctx.textBaseline = 'middle';
 
-  // Try full lines first, then stripped (prefix removed) if it doesn't fit
   for (const tryLines of [lines, stripped]) {
-    // Target font size: 14px, but scale down to fit
     let fontSize = 14;
     const lineCount = tryLines.length;
     const totalTextH = () => fontSize * lineCount + (lineCount - 1) * 1;
 
-    // Scale down if too tall
     while (totalTextH() > availH && fontSize > 4) fontSize -= 0.5;
 
-    // Scale down if too wide
     ctx.font = `bold ${fontSize}px Arial`;
     let maxW = Math.max(...tryLines.map(l => ctx.measureText(l).width));
     while (maxW > availW && fontSize > 4) {
@@ -588,6 +599,56 @@ function drawConveyanceLabel(ctx: CanvasRenderingContext2D, sym: PlacedSymbol) {
   }
 }
 
+/** Draw label along a curved symbol's arc band */
+function drawCurvedLabel(ctx: CanvasRenderingContext2D, sym: PlacedSymbol) {
+  if (!sym.label) return;
+  const { lines, stripped } = parseConveyanceLabel(sym.label);
+  const angle = sym.curveAngle || 90;
+  const { arcCx, arcCy, outerR, innerR, bandW } = getCurveGeometry(sym.symbolId, sym.x, sym.y, sym.w, sym.h);
+  const midR = (outerR + innerR) / 2;
+  const midAngleRad = ((angle / 2) * Math.PI) / 180; // half the sweep angle
+
+  // Position at arc midpoint
+  const textX = arcCx + midR * Math.cos(midAngleRad);
+  const textY = arcCy - midR * Math.sin(midAngleRad);
+  // Rotation: perpendicular to radius = tangent to arc
+  const textRot = -midAngleRad + Math.PI / 2;
+
+  const availW = bandW - 4;
+
+  ctx.save();
+  ctx.translate(textX, textY);
+  ctx.rotate(textRot);
+  ctx.fillStyle = '#000000';
+  ctx.textAlign = 'center';
+  ctx.textBaseline = 'middle';
+
+  for (const tryLines of [lines, stripped]) {
+    let fontSize = 14;
+    const lineCount = tryLines.length;
+    while (fontSize * lineCount > availW && fontSize > 4) fontSize -= 0.5;
+    ctx.font = `bold ${fontSize}px Arial`;
+    let maxW = Math.max(...tryLines.map(l => ctx.measureText(l).width));
+    // Available length along the arc at midR
+    const arcLen = midR * (angle * Math.PI / 180) * 0.6; // use 60% of arc
+    while (maxW > arcLen && fontSize > 4) {
+      fontSize -= 0.5;
+      ctx.font = `bold ${fontSize}px Arial`;
+      maxW = Math.max(...tryLines.map(l => ctx.measureText(l).width));
+    }
+    if (fontSize >= 4) {
+      const lineH = fontSize;
+      const startY = -(lineCount - 1) * lineH / 2;
+      for (let i = 0; i < tryLines.length; i++) {
+        ctx.fillText(tryLines[i], 0, startY + i * lineH);
+      }
+      ctx.restore();
+      return;
+    }
+  }
+  ctx.restore();
+}
+
 function drawSymbolOverlays(ctx: CanvasRenderingContext2D, sym: PlacedSymbol) {
   const cx = sym.x + sym.w / 2;
   const isSelected = layout.selectedIds.has(sym.id);