fix: surface silent scraper failures and stop falsely claiming weather delay

The homepage was flagging every park as weather delay because calendar.ts
collapsed "fetchLiveRides returned null" into the same openRides=0 bucket as
"all rides actually closed." Meanwhile every scraper (queuetimes, sixflags
operating-hours, sixflags wait-times) was swallowing non-OK responses and
exceptions silently, so logs gave no signal which upstream was failing or how.

Add a small scraperWarn helper that emits in the same shape as backend/log.ts
(without importing it — lib/scrapers is shared with the Next frontend). Use it
in all three scrapers to record HTTP status and error name+message before each
return null. Add parksSkipped to the tier-5 summary log so we can tell when the
openParks filter is rejecting everyone vs the fetcher silently failing.

Convert calendar.ts ridesCache to a discriminated union { kind: "ok" | "unknown" }.
Weather delay only fires on { kind: "ok", openRides: 0 }; unknown entries get
a 30s TTL so we recover quickly when upstream comes back and don't thunder-herd
in the meantime.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/scrapers/sixflags-waittimes.ts

@@ -12,6 +12,7 @@
  */
 
 import { normalizeForMatch } from "../coaster-match";
+import { scraperWarn } from "./log";
 
 const WAIT_TIMES_BASE = "https://d18car1k0ff81h.cloudfront.net/wait-times/park";
 
@@ -119,10 +120,23 @@ export async function fetchFastLaneWaits(
       signal: AbortSignal.timeout(10_000),
     } as RequestInit & { next: { revalidate: number } });
 
-    if (!res.ok) return null;
+    if (!res.ok) {
+      scraperWarn("sixflags-waittimes", "fetchFastLaneWaits non-OK response", {
+        apiId,
+        status: res.status,
+        statusText: res.statusText,
+      });
+      return null;
+    }
 
     return parseWaitTimes((await res.json()) as WTResponse);
-  } catch {
+  } catch (err) {
+    const e = err as Error;
+    scraperWarn("sixflags-waittimes", "fetchFastLaneWaits threw", {
+      apiId,
+      name: e.name,
+      err: e.message,
+    });
     return null;
   }
 }