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/investigations/[id]/report/page.jsx

@@ -9,6 +9,7 @@ export default function ReportPage() {
   const [hydrated, setHydrated] = useState(false);
   const [generationLoading, setGenerationLoading] = useState(false);
   const [generationError, setGenerationError] = useState(false);
+  const [updateLoading, setUpdateLoading] = useState(false);
 
   const generationAttempted = useRef(false);
 
@@ -66,6 +67,48 @@ export default function ReportPage() {
     })();
   }, [hydrated, existing]);
 
+  // Manual Report update (v0.59b — freshness manual update)
+  const handleUpdateReport = async () => {
+    if (updateLoading) return;
+    setUpdateLoading(true);
+
+    const snap = loadInvestigation();
+    const situationGraph = snap?.situationGraph;
+    const findings = snap?.findings ?? [];
+    const rev = snap?.investigationRevision ?? 0;
+
+    if (!situationGraph) {
+      setUpdateLoading(false);
+      return;
+    }
+
+    try {
+      const res = await fetch("/api/cases/overview", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify({ situationGraph, findings }),
+      });
+
+      if (!res.ok) {
+        setUpdateLoading(false);
+        return;
+      }
+
+      const data = await res.json();
+      if (data.success) {
+        const reportData = { understanding: data.understanding, plausibleInterpretations: data.plausibleInterpretations, hasPlausibleInterpretations: true, generatedFromRevision: rev };
+        setExisting((p) => {
+          saveInvestigation({ ...p, investigationReport: reportData });
+          return { ...p, investigationReport: reportData };
+        });
+      }
+    } catch {
+      /* failure: retain existing Report and updateAvailable state */
+    } finally {
+      setUpdateLoading(false);
+    }
+  };
+
   const report = existing?.investigationReport || null;
   const scenario = hydrated ? (existing?.scenario || "") : null;
 
@@ -79,6 +122,28 @@ export default function ReportPage() {
         Investigation Report
       </h1>
 
+      {/* Report freshness — only when a Report exists */}
+      {report ? (
+        <div className="mt-6 flex items-center gap-3">
+          {existing?.investigationRevision === report.generatedFromRevision ? (
+            <span className="text-[11px] font-semibold tracking-wider uppercase text-teal-700/70">Current</span>
+          ) : (
+            <div className="flex items-center gap-3">
+              <span className="text-[11px] font-semibold tracking-wider uppercase text-gray-500">Update available</span>
+              <span className="text-xs text-gray-400">The investigation has changed since this report was generated.</span>
+              <button
+                type="button"
+                onClick={handleUpdateReport}
+                disabled={updateLoading}
+                className="rounded-lg border border-teal-600 bg-white px-3 py-1.5 text-[11px] font-semibold tracking-wider uppercase text-teal-700 hover:bg-teal-50 transition disabled:opacity-40"
+              >
+                {updateLoading ? "Updating&#8230;" : "Update report"}
+              </button>
+            </div>
+          )}
+        </div>
+      ) : null}
+
       {/* Situation */}
       {scenario && (
         <div className="mt-8 rounded-xl border-[2.5px] border-teal-300/70 bg-gradient-to-b from-teal-50/60 to-white px-8 pt-6 pb-7 shadow-sm">

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