Fix Router→HBM_CTRL lines visibility in cube_view

Draw HBM connection lines last (on top of component blocks).
PE routers: thicker (1.5px, opacity 0.6) with dashed style.
Relay routers: thinner (0.7px, opacity 0.2).

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

src/kernbench/topology/visualizer.py

@@ -563,16 +563,7 @@ def _render_cube_view_svg(view: ViewGraph, spec: dict) -> str:
             f'{rkey}</text>'
         )
 
-        # ── Router → HBM_CTRL line (all routers connect to HBM) ──
-        hbm_edge_y = hbm_y if py < hbm_y else hbm_y + hbm_h
-        r_edge_y = py + r_size if py < hbm_y else py - r_size
-        # Only draw if not inside HBM zone
-        if abs(r_edge_y - hbm_edge_y) > 10:
-            parts.append(
-                f'  <line x1="{px:.0f}" y1="{r_edge_y:.0f}" '
-                f'x2="{px:.0f}" y2="{hbm_edge_y:.0f}" '
-                f'stroke="#10b981" stroke-width="0.8" opacity="0.25"/>'
-            )
+        # ── Router → HBM_CTRL line (deferred, drawn after component blocks) ──
 
         # ── Attached component blocks ──
         # Collect components to draw, positioned outward from router
@@ -672,14 +663,36 @@ def _render_cube_view_svg(view: ViewGraph, spec: dict) -> str:
 
         # ── PE router → HBM BW annotation ──
         if pe_items:
+            pe_hbm_edge = hbm_y if py < hbm_y else hbm_y + hbm_h
+            pe_r_edge = py + r_size if py < hbm_y else py - r_size
             bw_x = px + 14
-            bw_y = (r_edge_y + hbm_edge_y) / 2
+            bw_y = (pe_r_edge + pe_hbm_edge) / 2
             parts.append(
                 f'  <text x="{bw_x:.0f}" y="{bw_y:.0f}" '
                 f'font-family="monospace" font-size="6" fill="#10b98188">'
                 f'{agg_bw:.0f}GB/s</text>'
             )
 
+    # ── Router → HBM_CTRL lines (drawn last, on top of everything) ──
+    for rkey, rval in routers.items():
+        if rval is None:
+            continue
+        rx, ry = rval["pos_mm"]
+        px, py = mm2px(rx, ry)
+        hbm_edge_y = hbm_y if py < hbm_y else hbm_y + hbm_h
+        r_edge_y = py + r_size if py < hbm_y else py - r_size
+        if abs(r_edge_y - hbm_edge_y) > 10:
+            has_pe = any(a.endswith(".dma") for a in rval.get("attach", []))
+            # PE routers: thicker, more visible
+            sw = "1.5" if has_pe else "0.7"
+            op = "0.6" if has_pe else "0.2"
+            parts.append(
+                f'  <line x1="{px:.0f}" y1="{r_edge_y:.0f}" '
+                f'x2="{px:.0f}" y2="{hbm_edge_y:.0f}" '
+                f'stroke="#10b981" stroke-width="{sw}" opacity="{op}" '
+                f'stroke-dasharray="4,3"/>'
+            )
+
     # ── Legend ──
     ly = h_px - 35
     legend_items = [