fix: harden dark background — html + body + .post all set to var(--c-bg)

agentic-workflow.html

@@ -63,6 +63,8 @@
 
     *, *::before, *::after { box-sizing: border-box; }
 
+    html { background: var(--c-bg); }
+
     body {
       margin: 0;
       padding: 0;
@@ -76,6 +78,7 @@
 
     /* ── Post container ── */
     .post {
+      background: var(--c-bg);
       max-width: 720px;
       margin: 0 auto;
       padding: 48px 24px 60px;