Sync inbox hover with j/k selection

Hovering an inbox row now sets it as the selected index used by the
mail-client j/k keyboard shortcuts, so the keyboard cursor follows the
mouse instead of disagreeing with it.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/pages/Inbox.test.tsx

@@ -138,6 +138,11 @@ vi.mock("@/lib/router", () => ({
 // eslint-disable-next-line @typescript-eslint/no-explicit-any
 (globalThis as any).IS_REACT_ACT_ENVIRONMENT = true;
 
+// jsdom doesn't implement scrollIntoView; the inbox calls it from a passive effect.
+if (typeof Element !== "undefined" && !Element.prototype.scrollIntoView) {
+  Element.prototype.scrollIntoView = () => {};
+}
+
 function createIssue(overrides: Partial<Issue> = {}): Issue {
   return {
     id: "issue-1",
@@ -289,6 +294,59 @@ describe("Inbox toolbar", () => {
       root.unmount();
     });
   });
+
+  it("syncs hover with j/k selection on inbox rows", async () => {
+    routerMock.location.pathname = "/inbox/mine";
+    const issueA = createIssue({ id: "issue-a", identifier: "PAP-1001", title: "First inbox row" });
+    const issueB = createIssue({ id: "issue-b", identifier: "PAP-1002", title: "Second inbox row" });
+    apiMocks.issuesList.mockResolvedValue([issueA, issueB]);
+
+    const queryClient = new QueryClient({
+      defaultOptions: { queries: { retry: false, staleTime: 0, gcTime: 0 } },
+    });
+    const root = createRoot(container);
+
+    await act(async () => {
+      root.render(
+        <QueryClientProvider client={queryClient}>
+          <Inbox />
+        </QueryClientProvider>,
+      );
+    });
+    await act(async () => {
+      await Promise.resolve();
+    });
+
+    const rows = container.querySelectorAll("[data-inbox-item]");
+    expect(rows.length).toBeGreaterThanOrEqual(2);
+
+    const linkOf = (row: Element): HTMLAnchorElement | null =>
+      row.querySelector("a[data-inbox-issue-link]");
+
+    // Nothing selected before hover — both rows show the hover-accent class.
+    expect(linkOf(rows[0]!)?.className).toContain("hover:bg-accent/50");
+    expect(linkOf(rows[1]!)?.className).toContain("hover:bg-accent/50");
+
+    await act(async () => {
+      rows[1]!.dispatchEvent(new MouseEvent("mouseover", { bubbles: true }));
+    });
+
+    // After hovering row 1, that row is "selected" — same visual state as j/k selection.
+    expect(linkOf(rows[1]!)?.className).toContain("hover:bg-transparent");
+    expect(linkOf(rows[0]!)?.className).toContain("hover:bg-accent/50");
+
+    await act(async () => {
+      rows[0]!.dispatchEvent(new MouseEvent("mouseover", { bubbles: true }));
+    });
+
+    // Hovering a different row moves the selection to follow the mouse.
+    expect(linkOf(rows[0]!)?.className).toContain("hover:bg-transparent");
+    expect(linkOf(rows[1]!)?.className).toContain("hover:bg-accent/50");
+
+    act(() => {
+      root.unmount();
+    });
+  });
 });
 
 describe("FailedRunInboxRow", () => {

ui/src/pages/Inbox.tsx

@@ -2440,6 +2440,9 @@ export function Inbox() {
                         onClick={() => {
                           if (groupNavIdx >= 0) setSelectedIndex(groupNavIdx);
                         }}
+                        onMouseEnter={() => {
+                          if (groupNavIdx >= 0) setSelectedIndex(groupNavIdx);
+                        }}
                       >
                         <IssueGroupHeader
                           label={group.label}
@@ -2476,6 +2479,7 @@ export function Inbox() {
                         data-inbox-item
                         className="relative"
                         onClick={() => setSelectedIndex(navIdx)}
+                        onMouseEnter={() => setSelectedIndex(navIdx)}
                       >
                         {child}
                       </div>
@@ -2643,7 +2647,12 @@ export function Inbox() {
                             key={`sel-issue:${child.id}`}
                             data-inbox-item
                             className="relative"
-                            onClick={() => setSelectedIndex(childNavIdx)}
+                            onClick={() => {
+                              if (childNavIdx >= 0) setSelectedIndex(childNavIdx);
+                            }}
+                            onMouseEnter={() => {
+                              if (childNavIdx >= 0) setSelectedIndex(childNavIdx);
+                            }}
                           >
                             {canArchiveIssue ? (
                               <SwipeToArchive