fix: resolve queued stream metadata in the background

Queue labels were only enriched through selected-entry playback. Resolve unplayed titles serially at utility priority, preempt enrichment for playback, and bind updates to queue item IDs.

Verified: make check-resolved check-queue check-youtube all.

Sources/App/YouTubeResolver.swift

@@ -312,7 +312,7 @@ private struct YouTubeExtractionOutput: Sendable {
 
 // All Process, pipe, and continuation state belongs to this request's serial queue.
 private final class YouTubeExtraction: @unchecked Sendable {
-    private let queue = DispatchQueue(label: "terebi.youtube-extraction", qos: .userInitiated)
+    private let queue: DispatchQueue
     private let process = Process()
     private let stdoutPipe = Pipe()
     private let stderrPipe = Pipe()
@@ -331,6 +331,9 @@ private final class YouTubeExtraction: @unchecked Sendable {
     private var failure: (any Error)?
 
     init(executable: URL, arguments: [String], environment: [String: String]) {
+        let background = Task.currentPriority <= .utility
+        queue = DispatchQueue(label: "terebi.youtube-extraction", qos: background ? .utility : .userInitiated)
+        process.qualityOfService = background ? .utility : .userInitiated
         process.executableURL = executable
         process.arguments = arguments
         process.environment = environment