style(m7): plain executed_at field at the top, no red sub-card

User feedback: the tinted red border around the executed_at block was
visually heavy — same form-field treatment as Command/Output/Comment
is enough, position alone carries the priority.

Kept the label/value/override-toggle/datetime-input layout, just dropped
the border + background tint.

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

frontend/src/pages/MissionTestPage.tsx

@@ -247,34 +247,30 @@ function RedZone({ test, missionId, canWriteRed }: RedZoneProps) {
       <SectionHeader prefix="Red" highlight="Execution" accent="red" />
       {apiErr && <Alert accent="red">{apiErr.message}</Alert>}
 
-      {/* The execution timestamp is the anchor the blue team correlates their
-          logs against, so it lives at the very top of the form (cf. user
-          feedback 2026-05-15). */}
-      <div
-        className="rounded-md border border-red/40 bg-red/5 p-3"
-        data-testid="red-executed-block"
-      >
-        <div className="flex flex-wrap items-baseline justify-between gap-2 mb-2">
-          <span className="font-mono text-2xs uppercase tracking-wider2 text-red">
-            Executed at
-          </span>
+      {/* The execution timestamp anchors the blue team's log correlation,
+          so it leads the form (cf. user feedback 2026-05-15). */}
+      <div data-testid="red-executed-block">
+        <span className="block font-mono text-3xs font-semibold uppercase tracking-wider2 text-text-dim">
+          Executed at
+        </span>
+        <p
+          className="mt-1 font-mono text-xs text-text-bright"
+          data-testid="red-executed-current"
+        >
           {test.executed_at ? (
-            <code
-              className="font-mono text-2xs text-text-bright"
-              data-testid="red-executed-current"
-            >
-              {test.executed_at}
+            <>
+              <code>{test.executed_at}</code>
               {test.executed_at_overridden && (
                 <span className="ml-2 text-text-dim">· overridden</span>
               )}
-            </code>
+            </>
           ) : (
-            <span className="font-mono text-2xs text-text-dim">
+            <span className="text-text-dim">
               Not yet executed — use the "→ Executed" transition above to stamp.
             </span>
           )}
-        </div>
-        <label className="flex items-center gap-2 font-mono text-2xs text-text-dim">
+        </p>
+        <label className="mt-2 flex items-center gap-2 font-mono text-2xs text-text-dim">
           <input
             type="checkbox"
             checked={override}