fix(desktop): use two-tier ink in agent graph metadata

The ink-ladder contract retires --foreground-secondary; secondary metadata text takes --muted-foreground.

Generated-by: Muse Spark

Author: orangeCatDeveloper

apps/desktop/src/renderer/styles/agent-graph.css

@@ -304,7 +304,7 @@
 .maka-agent-graph-details-metadata dd {
   min-width: 0;
   margin: 0;
-  color: var(--foreground-secondary);
+  color: var(--muted-foreground);
   overflow-wrap: anywhere;
 }