style(notifications): the Earlier fold reads as a section heading, like its siblings

It was a ghost button in body type under two uppercase section labels. It is now
the heading itself, its text the disclosure's button (24px tall, past the
WCAG 2.5.8 floor).

frontend/src/modules/notifications/NotificationsPanel.order.dom.test.tsx

@@ -139,6 +139,8 @@ describe("NotificationsPanel · order", () => {
     expect(rows()).toEqual(["Ready 1"]);
     const fold = screen.getByRole("button", { name: "inbox.earlier:2" });
     expect(fold.getAttribute("aria-expanded")).toBe("false");
+    // A section heading like "Needs you" and "Recent", its text the disclosure's button.
+    expect(fold.closest("h2")).not.toBeNull();
     fireEvent.click(fold);
     expect(fold.getAttribute("aria-expanded")).toBe("true");
     expect(rows()).toEqual(["Ready 1", "Activity 3", "Ready 2"]);

frontend/src/modules/notifications/NotificationsPanel.tsx

@@ -46,6 +46,7 @@ import { channelYouTubeUrl, formatDate } from "../../lib/format";
 import { entryKey, keyOf, orderInbox, type InboxEntry } from "../../lib/inboxOrder";
 import { Button } from "../../components/ui/Button";
 import { IconButton } from "../../components/ui/IconButton";
+import { Pressable } from "../../components/ui/Pressable";
 import { LEVEL_STYLE } from "../../components/ui/toastLevels";
 import { PageToolbar } from "../../components/ui/PageShell";
 import { PageMenu } from "../../components/ui/PageMenu";
@@ -481,16 +482,22 @@ export default function NotificationsPanel() {
             )}
             {order.earlier.length > 0 && (
               <section>
-                <Button
-                  variant="ghost"
-                  size="sm"
-                  aria-expanded={earlierOpen}
-                  onClick={() => setEarlierOpen((o) => !o)}
-                  icon={earlierOpen ? <ChevronDown /> : <ChevronRight />}
-                  className={earlierOpen ? "mb-2" : undefined}
-                >
-                  {t("inbox.earlier", { count: order.earlier.length })}
-                </Button>
+                {/* A heading like its siblings, its text the disclosure's button (the ARIA
+                    disclosure pattern); 24px tall so the target clears the WCAG 2.5.8 floor. */}
+                <SectionLabel className={earlierOpen ? "mb-2" : undefined}>
+                  <Pressable
+                    aria-expanded={earlierOpen}
+                    onClick={() => setEarlierOpen((o) => !o)}
+                    className="min-h-6 inline-flex items-center gap-1 uppercase hover:text-fg transition"
+                  >
+                    {earlierOpen ? (
+                      <ChevronDown className="size-3.5" aria-hidden />
+                    ) : (
+                      <ChevronRight className="size-3.5" aria-hidden />
+                    )}
+                    {t("inbox.earlier", { count: order.earlier.length })}
+                  </Pressable>
+                </SectionLabel>
                 {earlierOpen && (
                   <NavGrid className="flex flex-col gap-2">{order.earlier.map(entry)}</NavGrid>
                 )}