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/db.ts

@@ -13,11 +13,12 @@ export function openDb(): Database.Database {
   db.pragma("journal_mode = WAL");
   db.exec(`
     CREATE TABLE IF NOT EXISTS park_days (
-      park_id    TEXT    NOT NULL,
-      date       TEXT    NOT NULL,  -- YYYY-MM-DD
-      is_open    INTEGER NOT NULL DEFAULT 0,
-      hours_label TEXT,
-      scraped_at TEXT    NOT NULL,
+      park_id      TEXT    NOT NULL,
+      date         TEXT    NOT NULL,  -- YYYY-MM-DD
+      is_open      INTEGER NOT NULL DEFAULT 0,
+      hours_label  TEXT,
+      special_type TEXT,              -- 'passholder_preview' | null
+      scraped_at   TEXT    NOT NULL,
       PRIMARY KEY (park_id, date)
     );
     CREATE TABLE IF NOT EXISTS park_api_ids (
@@ -28,6 +29,12 @@ export function openDb(): Database.Database {
       discovered_at    TEXT NOT NULL
     )
   `);
+  // Migrate existing databases that predate the special_type column
+  try {
+    db.exec(`ALTER TABLE park_days ADD COLUMN special_type TEXT`);
+  } catch {
+    // Column already exists — safe to ignore
+  }
   return db;
 }
 
@@ -36,21 +43,24 @@ export function upsertDay(
   parkId: string,
   date: string,
   isOpen: boolean,
-  hoursLabel?: string
+  hoursLabel?: string,
+  specialType?: string
 ) {
   db.prepare(`
-    INSERT INTO park_days (park_id, date, is_open, hours_label, scraped_at)
-    VALUES (?, ?, ?, ?, ?)
+    INSERT INTO park_days (park_id, date, is_open, hours_label, special_type, scraped_at)
+    VALUES (?, ?, ?, ?, ?, ?)
     ON CONFLICT (park_id, date) DO UPDATE SET
-      is_open     = excluded.is_open,
-      hours_label = excluded.hours_label,
-      scraped_at  = excluded.scraped_at
-  `).run(parkId, date, isOpen ? 1 : 0, hoursLabel ?? null, new Date().toISOString());
+      is_open      = excluded.is_open,
+      hours_label  = excluded.hours_label,
+      special_type = excluded.special_type,
+      scraped_at   = excluded.scraped_at
+  `).run(parkId, date, isOpen ? 1 : 0, hoursLabel ?? null, specialType ?? null, new Date().toISOString());
 }
 
 export interface DayData {
   isOpen: boolean;
   hoursLabel: string | null;
+  specialType: string | null;
 }
 
 /**
@@ -65,7 +75,7 @@ export function getDateRange(
 ): Record<string, Record<string, DayData>> {
   const rows = db
     .prepare(
-      `SELECT park_id, date, is_open, hours_label
+      `SELECT park_id, date, is_open, hours_label, special_type
        FROM park_days
        WHERE date >= ? AND date <= ?`
     )
@@ -74,6 +84,7 @@ export function getDateRange(
     date: string;
     is_open: number;
     hours_label: string | null;
+    special_type: string | null;
   }[];
 
   const result: Record<string, Record<string, DayData>> = {};
@@ -82,6 +93,7 @@ export function getDateRange(
     result[row.park_id][row.date] = {
       isOpen: row.is_open === 1,
       hoursLabel: row.hours_label,
+      specialType: row.special_type,
     };
   }
   return result;