fix: clean up launcher tmp/bindable items; update TODO

- Update stale comment in menu_location_list.svelte: prop is already
  $bindable(null), comment incorrectly said it was not
- Confirm cleanup_tmp_files is wired in launcher_background_sync.svelte
- Mark both items done in TODO__Agents.md

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

@@ -20,11 +20,9 @@
      *   → navigates to /launcher/{location_id} via goto()
      *
      * NOTE — slct_event_location_id binding:
-     *   This prop is NOT declared $bindable() but is used with bind:value on the <select>.
-     *   This is intentional: the onchange handler writes directly to the canonical stores
-     *   ($events_slct.event_location_id) rather than propagating through a prop binding.
-     *   The bind:value keeps the select's visual state in sync with the store value passed
-     *   in from the parent without requiring a two-way prop binding.
+     *   Declared $bindable() so the parent can pass the initial selected value via bind:.
+     *   The onchange handler also writes directly to the canonical stores
+     *   ($events_slct.event_location_id) to keep other parts of the launcher in sync.
      */
     interface Props {
         loading__session_li_status?: null | boolean | string;