fix(ui): settle superseded preview requests silently

A preview left in flight across a structural configuration change could
still publish its result or error, so the page described a package that
was no longer selected. Previews now carry a request generation that
structural changes bump: a superseded preview keeps its progress panel
while running (imports and previews stay attached per the earlier fix)
but settles silently — no stale preview render, error panel, or toast.
Imports are deliberately not gated: they mutate the server, so their
outcome is always published. Component tests cover the silent settle and
the current-request failure path.

ui/src/pages/CompanyImport.test.tsx

@@ -346,8 +346,9 @@ describe("CompanyImport", () => {
     expect(container.textContent).toContain("Uploading and analyzing your package");
     expect(container.textContent).toContain("Keep this page open.");
 
-    // Config edits while the request is in flight must not detach it from
-    // the UI: the progress panel keeps reporting it until it settles.
+    // A mid-flight config edit keeps the progress panel visible (the request
+    // really is still running) but supersedes the request, so its failure
+    // settles silently instead of describing a package no longer selected.
     await enterGithubUrl("https://github.com/acme/starter-b/tree/main/company");
 
     expect(container.textContent).toContain("Uploading and analyzing your package");
@@ -358,6 +359,16 @@ describe("CompanyImport", () => {
     await flushReact();
 
     expect(container.textContent).not.toContain("Uploading and analyzing your package");
+    expect(container.textContent).not.toContain("Preview failed:");
+    expect(mockPushToast).not.toHaveBeenCalled();
+
+    // A failure of the currently configured request renders a durable panel.
+    await clickButton((text) => text === "Preview import");
+    await act(async () => {
+      rejectPreview(new Error("stream disconnected"));
+    });
+    await flushReact();
+
     expect(container.textContent).toContain("Preview failed: stream disconnected");
     expect(container.textContent).toContain("Retry, or use the CLI folder import");
     expect(mockPushToast).toHaveBeenCalledWith(expect.objectContaining({ tone: "error" }));

ui/src/pages/CompanyImport.tsx

@@ -770,9 +770,16 @@ export function CompanyImport() {
     return { type: "github", url };
   }
 
+  // Monotonic id for preview requests. Structural configuration changes bump
+  // it, so an in-flight preview they supersede settles silently instead of
+  // publishing a result or error for a package that is no longer selected.
+  // Imports are not gated this way: they mutate the server, so their outcome
+  // is always published.
+  const previewGenerationRef = useRef(0);
+
   // Preview mutation
   const previewMutation = useMutation({
-    mutationFn: () => {
+    mutationFn: (_generation: number) => {
       const source = buildSource();
       if (!source) throw new Error("No source configured.");
       return companiesApi.importPreview({
@@ -785,7 +792,8 @@ export function CompanyImport() {
         collisionStrategy,
       });
     },
-    onSuccess: (result) => {
+    onSuccess: (result, generation) => {
+      if (generation !== previewGenerationRef.current) return;
       setImportPreview(result);
 
       // Build conflicts and set default name overrides with prefix
@@ -848,7 +856,8 @@ export function CompanyImport() {
       const firstFile = Object.keys(result.files)[0];
       if (firstFile) setSelectedFile(firstFile);
     },
-    onError: (err) => {
+    onError: (err, generation) => {
+      if (generation !== previewGenerationRef.current) return;
       pushToast({
         tone: "error",
         title: "Preview failed",
@@ -939,6 +948,7 @@ export function CompanyImport() {
   }
 
   function resetImportFlowState() {
+    previewGenerationRef.current += 1;
     setImportPreview(null);
     resetMutationState();
   }
@@ -1457,7 +1467,7 @@ export function CompanyImport() {
           <Button
             size="sm"
             variant="outline"
-            onClick={() => previewMutation.mutate()}
+            onClick={() => previewMutation.mutate(previewGenerationRef.current)}
             disabled={previewMutation.isPending || !hasSource || inlineImportBlocked}
           >
             {previewMutation.isPending ? "Previewing..." : "Preview import"}
@@ -1483,7 +1493,9 @@ export function CompanyImport() {
             </p>
           </div>
         )}
-        {previewMutation.isError && !previewMutation.isPending && (
+        {previewMutation.isError &&
+          !previewMutation.isPending &&
+          previewMutation.variables === previewGenerationRef.current && (
           <div className="mt-3 rounded-md border border-destructive/40 bg-destructive/5 px-3 py-2.5">
             <p className="text-xs text-destructive">
               Preview failed:{" "}