paper(ipcq): de-emphasize flow-diagram outer frame so inner flow stands out

Drops the per-case panel outline from linewidth 2.2 to 0.9 with 85% alpha.
The case-color frame still anchors each panel but no longer competes
with the swimlanes, flit packets, and annotations inside.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

scripts/paper/paper_plot_ipcq_alternatives_comparison.py

@@ -290,11 +290,12 @@ def _flow_lead(ax, x_tail, y_tail, x_head, y_head, color="#777"):
 
 def _flow_setup(ax, kind):
     ax.set_xlim(0, 20); ax.set_ylim(0, 10); ax.axis("off")
+    # Thin, subtle outer frame so the per-case flow inside dominates.
     ax.add_patch(mpatches.FancyBboxPatch(
         (0.15, 0.15), 19.7, 9.7,
         boxstyle="round,pad=0.05,rounding_size=0.12",
         facecolor="white", edgecolor=_COLOR[kind],
-        linewidth=2.2, zorder=0))
+        linewidth=0.9, alpha=0.85, zorder=0))
     ax.text(10, 0.65, _TITLE[kind],
             ha="center", va="center", fontsize=11.5,
             fontweight="bold",