Harmonize Graphviz diagrams with the ARCP design system

Mechanical restyle applied to every .dot/.svg pair:
- fontname: Helvetica/Inter → TT Commons Pro Trial
- splines: ortho → spline (curved edges)
- shape=ellipse → shape=box with style="rounded[,filled]"

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: nficano

docs/diagrams/capability-negotiation-dark.dot

@@ -4,7 +4,7 @@ digraph CapabilityNegotiation {
   rankdir=LR;
   bgcolor="transparent";
   compound=true;
-  fontname="Helvetica";
+  fontname="TT Commons Pro Trial";
   splines=spline;
   nodesep=0.40;
   ranksep=0.70;
@@ -15,14 +15,14 @@ digraph CapabilityNegotiation {
     style="rounded,filled",
     fillcolor="#334155",
     color="#475569",
-    fontname="Helvetica",
+    fontname="TT Commons Pro Trial",
     fontsize=11,
     fontcolor="#F1F5F9",
     margin="0.22,0.11",
     penwidth=1.0
   ];
   edge [
-    fontname="Helvetica",
+    fontname="TT Commons Pro Trial",
     fontsize=9,
     fontcolor="#94A3B8",
     color="#64748B",
@@ -42,7 +42,7 @@ digraph CapabilityNegotiation {
     style="rounded,filled";
     fillcolor="#0F172A";
     color="#334155";
-    fontname="Helvetica";
+    fontname="TT Commons Pro Trial";
     fontcolor="#94A3B8";
     margin=14;
     labeljust=l;

docs/diagrams/capability-negotiation-dark.svg

@@ -4,7 +4,7 @@ digraph CapabilityNegotiation {
   rankdir=LR;
   bgcolor="transparent";
   compound=true;
-  fontname="Helvetica";
+  fontname="TT Commons Pro Trial";
   splines=spline;
   nodesep=0.40;
   ranksep=0.70;
@@ -15,14 +15,14 @@ digraph CapabilityNegotiation {
     style="rounded,filled",
     fillcolor="white",
     color="#CBD5E1",
-    fontname="Helvetica",
+    fontname="TT Commons Pro Trial",
     fontsize=11,
     fontcolor="#1F2937",
     margin="0.22,0.11",
     penwidth=1.0
   ];
   edge [
-    fontname="Helvetica",
+    fontname="TT Commons Pro Trial",
     fontsize=9,
     fontcolor="#64748B",
     color="#94A3B8",
@@ -42,7 +42,7 @@ digraph CapabilityNegotiation {
     style="rounded,filled";
     fillcolor="#F1F5F9";
     color="#E2E8F0";
-    fontname="Helvetica";
+    fontname="TT Commons Pro Trial";
     fontcolor="#475569";
     margin=14;
     labeljust=l;