feat(verification): acceptance-check layer + executor fix-loop; hide phase-checkpoint walls; guaranteed turn-end summary. Verification gated behind VIBN_VERIFICATION_ENABLED.

vibn-frontend/components/vibn-chat/chat-panel.tsx

@@ -551,9 +551,17 @@ function ThinkingBubble({ thoughts }: { thoughts: string }) {
 
 function stripRawToolLogs(text: string): string {
   if (!text) return text;
-  return text
-    .replace(/(?:\r?\n)*\[tools executed this turn:[\s\S]*?\]/g, "")
-    .trim();
+  let out = text.replace(
+    /(?:\r?\n)*\[tools executed this turn:[\s\S]*?\]/g,
+    "",
+  );
+  // Safety net: strip the internal "Phase Checkpoint" planning block
+  // (Goal / Current Findings / Suspected Cause / Verification Plan) if it
+  // ever reaches a user-facing message. This is loop-control machinery, not
+  // something the end user should read. We drop from the heading to the end
+  // of that block (until a blank line followed by non-bulleted prose, or EOF).
+  out = out.replace(/(?:^|\n)\s*#{0,3}\s*Phase Checkpoint[\s\S]*$/i, "").trim();
+  return out.trim();
 }
 
 const MessageBubble = React.memo(function MessageBubble({
@@ -748,32 +756,8 @@ function Timeline({ entries }: { entries: TimelineEntry[] }) {
           );
         }
         if (item.kind === "checkpoint") {
-          return (
-            <div
-              key={i}
-              style={{
-                margin: "6px 0 12px",
-                padding: "12px 14px",
-                background: "oklch(0.20 0.04 35 / 0.15)",
-                border: "1px dashed var(--accent)",
-                borderRadius: 8,
-                fontSize: "0.75rem",
-                color: "var(--fg-mute)",
-                fontFamily: "var(--font-mono), monospace",
-              }}
-            >
-              <div
-                style={{
-                  color: "var(--accent)",
-                  fontWeight: "bold",
-                  marginBottom: 4,
-                }}
-              >
-                [Checkpoint Logged]
-              </div>
-              <div style={{ opacity: 0.8 }}>{item.goal}</div>
-            </div>
-          );
+          // Internal loop-control machinery — never shown to the user.
+          return null;
         }
         return (
           <TimelineToolGroup