feat(desktop): broaden hotkey coverage + fold in stray shortcuts

Add rebindable actions for the high-frequency gaps: focus composer, open
model picker, next/prev session, search sessions (⌘⇧F), show files/
terminal tab, and nav→artifacts. Reconcile the duplicate Shift+N new-
session listener into session.new's defaults, and surface the remaining
context-local shortcuts (⌘↵ steer, ⌘L terminal selection, ⌘W close
preview) as read-only rows so the panel is the honest source of truth.

apps/desktop/src/store/layout.ts

@@ -81,6 +81,22 @@ export function toggleFileBrowserOpen() {
   togglePane(FILE_BROWSER_PANE_ID)
 }
 
+export function setFileBrowserOpen(open: boolean) {
+  setPaneOpen(FILE_BROWSER_PANE_ID, open)
+}
+
+// Hotkey → focus the sessions search field. Opens the sidebar first, then lets
+// the field (which only mounts when the sidebar is open) subscribe + focus.
+export const SESSION_SEARCH_FOCUS_EVENT = 'hermes:focus-session-search'
+
+export function requestSessionSearchFocus() {
+  setSidebarOpen(true)
+
+  if (typeof window !== 'undefined') {
+    window.setTimeout(() => window.dispatchEvent(new CustomEvent(SESSION_SEARCH_FOCUS_EVENT)), 0)
+  }
+}
+
 export function togglePanesFlipped() {
   $panesFlipped.set(!$panesFlipped.get())
 }