fix(badges): throughput — weekday-first date header, keyed each block

Separators now read "Tuesday · June 9 — EDT" so day-of-week is the
lead identifier, matching how conference staff refer to the schedule.
Added key (sz) to the window-size each block.

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

src/routes/events/[event_id]/(badges)/badges/reports/reports_badge_print_throughput.svelte

@@ -40,12 +40,9 @@ const tz_abbr: string =
         .find((p) => p.type === 'timeZoneName')?.value ?? '';
 
 function fmt_date_header(ms: number): string {
-    const date_part = new Intl.DateTimeFormat('en-US', {
-        weekday: 'long',
-        month: 'long',
-        day: 'numeric'
-    }).format(ms);
-    return tz_abbr ? `${date_part} — ${tz_abbr}` : date_part;
+    const weekday = new Intl.DateTimeFormat('en-US', { weekday: 'long' }).format(ms);
+    const date_part = new Intl.DateTimeFormat('en-US', { month: 'long', day: 'numeric' }).format(ms);
+    return tz_abbr ? `${weekday} · ${date_part} — ${tz_abbr}` : `${weekday} · ${date_part}`;
 }
 
 // Naive UTC strings from the backend have no timezone indicator — append Z so
@@ -125,7 +122,7 @@ function get_effective_name(badge: any): string {
     <div class="flex flex-row flex-wrap items-center gap-3">
         <div class="flex flex-row items-center gap-1">
             <span class="text-sm text-surface-600-400">Window:</span>
-            {#each ([5, 15, 30, 60] as BucketMin[]) as sz}
+            {#each ([5, 15, 30, 60] as BucketMin[]) as sz (sz)}
                 <button
                     type="button"
                     onclick={() => { bucket_size = sz; expanded_bucket = null; }}