fix(live-tv): honour Cmd/Ctrl+B on collection pages and hide the header rail toggle on phones

Codex review follow-ups on #1555:

- The hidden-list state advertises Cmd/Ctrl+B, but the favorites/recent
  collection page had no handler; only the routed M3U/Xtream/Stalker live
  layouts did. The page now toggles the collection surface while its live
  tab is on screen, with the same typing/inert guards as the other hosts.
- At the phone breakpoint the header already holds the drawer toggle,
  switcher, search and Add; the live rail is a bottom drawer with its own
  toggle there, so the header rail toggle is hidden below 640px.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

libs/workspace/shell/feature/src/lib/workspace-shell/components/workspace-shell-header/workspace-shell-header.component.scss

@@ -398,5 +398,12 @@
         .shortcuts-trigger {
             display: none;
         }
+
+        // At the phone breakpoint the live rail is a bottom drawer with its
+        // own toggle, and the header has no room left for another permanent
+        // icon: it already holds the drawer toggle, switcher, search and Add.
+        .header-sidebar-toggle {
+            display: none;
+        }
     }
 }