feat(ui): a visible way into the command palette

Ctrl/Cmd+K and the shortcut sheet had no entry point but a palette row, behind the other
undiscoverable chord. Owner's pick from the S7 mockups (2026-09-19): a key cap at the end of the
header's search field opens the palette, and a page with no search field shows a small "Jump to…"
pill with the same key cap in its place, so the entry is on every page. The cap reads the chord the
palette row binds from the keymap table (Ctrl K, or ⌘ K on a Mac) and stays out of a phone's
header, where there is no keyboard to press it on.

frontend/src/components/Header.tsx

@@ -12,6 +12,7 @@ import { useNavigation } from "./navigationContext";
 import { useFeedFilters, useFeedFiltersActions } from "./feedFiltersContext";
 import { usePlaylists, usePlaylistsActions } from "./playlistsContext";
 import { useChannels, useChannelsActions } from "./channelsContext";
+import { PaletteLauncher } from "./PaletteLauncher";
 
 // The floating top header: a row of glass pills over the content — the module's SearchBar where it
 // has one, and the per-user sync chip at the right end.
@@ -42,7 +43,8 @@ const Header = forwardRef<
   const blur = () => (document.activeElement as HTMLElement | null)?.blur?.();
 
   // Per-page SearchBar wiring — null for modules without a search.
-  let search: ReactNode = null;
+  // A page without a search field still gets the palette's entry (PaletteLauncher).
+  let search: ReactNode = <PaletteLauncher />;
   if (page === "feed") {
     const trimmed = filters.q.trim();
     search = (