fix: Launcher dead-code cleanup — dead else-if branch and unused handle_get_device_info

- launcher/+layout.svelte: dead {:else if $events_slct.event_session_id} branch
  (condition identical to preceding {#if}) replaced with correct
  {:else if $events_slct.event_location_id} — shows "Select a session"
  prompt when a room is chosen but no session is yet selected.

- launcher/[event_location_id]/+page.svelte: removed unreachable
  handle_get_device_info() function (never called; pre-relay pattern
  superseded by launcher_background_sync.svelte's run_device_heartbeat()).
  Cleaned up now-unused imports.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/events/[event_id]/(launcher)/launcher/+layout.svelte

@@ -625,12 +625,13 @@
                 <Launcher_session_view
                     bind:slct__event_session_id={$events_slct.event_session_id}
                 ></Launcher_session_view>
-            {:else if $events_slct.event_session_id}
+            {:else if $events_slct.event_location_id}
+                <!-- Location selected but no session chosen yet — prompt operator -->
                 <div
                     class="flex flex-col items-center justify-center p-8 opacity-50"
                 >
                     <LoaderCircle class="animate-spin mb-2" />
-                    <span>Loading session details...</span>
+                    <span>Select a session from the menu</span>
                 </div>
             {/if}
         </section>