feat(confidence-engine): v0.59b-c — report freshness on Report page + Portfolio

v0.59b — Report page freshness UI:
- Shows Current / Update available beside the generated report
- Manual Update report action with duplicate prevention guard
- Explanation copy about investigation changes since generation
- Persists generatedFromRevision during update flow

v0.59c — Portfolio Report freshness state:
- Surfaces Current / Update available alongside existing View report link
- Derives solely from revision provenance (zero model calls)
- No Update report action on Portfolio (manual update owned by Report page)
- Neither state shown when no Report exists
- Updated makeSnapshot with investigationRevision for realistic test data

app/page.jsx

@@ -18,6 +18,11 @@ function Portfolio() {
     existing?.investigationReport && existing.investigationReport.understanding
   );
 
+  const reportIsCurrent =
+    hasReport &&
+    existing.investigationReport.generatedFromRevision ===
+      (existing.investigationRevision ?? 0);
+
   return (
     <main className="mx-auto max-w-[640px] px-6 py-16">
       <h1 className="mb-2 text-3xl font-bold tracking-tight">Confidence Engine</h1>
@@ -39,12 +44,24 @@ function Portfolio() {
 
             <div className="mt-4 flex gap-3 text-sm">
               {hasReport ? (
-                <Link
-                  href={`/investigations/${INVESTIGATION_ID}/report`}
-                  className="rounded-lg border border-teal-600 bg-white px-4 py-2 font-medium text-teal-700 hover:bg-teal-50 transition"
-                >
-                  View report
-                </Link>
+                <div className="flex items-center gap-2">
+                  <Link
+                    href={`/investigations/${INVESTIGATION_ID}/report`}
+                    className="rounded-lg border border-teal-600 bg-white px-4 py-2 font-medium text-teal-700 hover:bg-teal-50 transition"
+                  >
+                    View report
+                  </Link>
+
+                  {reportIsCurrent ? (
+                    <span className="text-[11px] font-semibold tracking-wider uppercase text-teal-700/70">
+                      Current
+                    </span>
+                  ) : (
+                    <span className="text-[11px] font-semibold tracking-wider uppercase text-gray-500">
+                      Update available
+                    </span>
+                  )}
+                </div>
               ) : null}
 
               <Link