feat: detect passholder preview days and filter plain buyouts

- Buyout days are now treated as closed unless they carry a Passholder
  Preview event, in which case they surface as a distinct purple cell
  in the UI showing "Passholder" + hours
- DB gains a special_type column (auto-migrated on next startup)
- scrape.ts threads specialType through to upsertDay
- debug.ts now shows events, isBuyout, isPassholderPreview, and
  specialType in the parsed result section

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

lib/scrapers/sixflags.ts

@@ -34,6 +34,7 @@ export interface DayResult {
   date: string; // YYYY-MM-DD
   isOpen: boolean;
   hoursLabel?: string;
+  specialType?: "passholder_preview";
 }
 
 function sleep(ms: number) {
@@ -49,6 +50,7 @@ function parseApiDate(d: string): string {
 interface ApiOperatingItem {
   timeFrom: string; // "10:30" 24h
   timeTo: string;   // "20:00" 24h
+  isBuyout?: boolean;
 }
 
 interface ApiOperating {
@@ -56,9 +58,14 @@ interface ApiOperating {
   items: ApiOperatingItem[];
 }
 
+interface ApiEvent {
+  extEventName: string;
+}
+
 interface ApiDay {
   date: string;
   isParkClosed: boolean;
+  events?: ApiEvent[];
   operatings?: ApiOperating[];
 }
 
@@ -135,9 +142,18 @@ export async function scrapeMonth(
       item?.timeFrom && item?.timeTo
         ? `${fmt24(item.timeFrom)} – ${fmt24(item.timeTo)}`
         : undefined;
-    // If the API says open but no hours are available, treat as closed
-    const isOpen = !d.isParkClosed && hoursLabel !== undefined;
-    return { date, isOpen, hoursLabel };
+
+    const isPassholderPreview = d.events?.some((e) =>
+      e.extEventName.toLowerCase().includes("passholder preview")
+    ) ?? false;
+
+    const isBuyout = item?.isBuyout ?? false;
+
+    // Buyout days are private events — treat as closed unless it's a passholder preview
+    const isOpen = !d.isParkClosed && hoursLabel !== undefined && (!isBuyout || isPassholderPreview);
+    const specialType: DayResult["specialType"] = isPassholderPreview ? "passholder_preview" : undefined;
+
+    return { date, isOpen, hoursLabel: isOpen ? hoursLabel : undefined, specialType };
   });
 }