fix: make release loading resilient to individual fetch failures (#9)

A missing data file (macOS-26.4-25E5223i.json) caused fetchAllReleases()
to fail entirely, showing zero releases in the app. Switch from
withThrowingTaskGroup to withTaskGroup so individual failures are logged
and skipped instead of aborting the whole load.

Also add the missing Tahoe 26.4 beta 3 data file.

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: p-linnane

Sources/macOSdbKit/DataProvider.swift

@@ -62,16 +62,25 @@ public actor DataProvider {
     public func fetchAllReleases() async throws -> [Release] {
         let index = try await fetchReleaseIndex()
 
-        return try await withThrowingTaskGroup(of: Release.self, returning: [Release].self) { group in
+        return await withTaskGroup(of: Release?.self, returning: [Release].self) { group in
             for entry in index {
                 group.addTask {
-                    try await self.fetchRelease(entry)
+                    do {
+                        return try await self.fetchRelease(entry)
+                    } catch {
+                        Self.logger.error(
+                            "Skipping \(entry.osVersion) (\(entry.buildNumber)): \(error.localizedDescription)"
+                        )
+                        return nil
+                    }
                 }
             }
 
             var releases: [Release] = []
-            for try await release in group {
-                releases.append(release)
+            for await release in group {
+                if let release {
+                    releases.append(release)
+                }
             }
             return releases.sorted()
         }