Add spoken exercise instructions (on-device TTS)

Speak exercise setup and form cues aloud with AVSpeechSynthesizer:

- Library detail: a speaker toolbar button reads the full reference aloud.
- Active workout: an opt-in "Speak Exercise Cues" setting speaks a brief
  cue (Setup/Execution/Cues) when an exercise starts, hands-free.
- Settings › Voice: pick the voice (auto-prefers an installed enhanced/
  premium English voice), a premium-download nudge shown only while on a
  basic voice, and a Speed/Pitch/Volume sheet with Reset to Defaults.

On-device and offline; ducks other audio rather than stopping it. iPhone
only for now. Shared SpeechSettings is the single source of truth for the
voice/prosody, read fresh per utterance so changes preview live.

Claude-Session: https://claude.ai/code/session_01BQcEWmAPA78338QuEwRkAh

Workouts/Speech/SpeechSettings.swift

@@ -0,0 +1,121 @@
+//
+// SpeechSettings.swift
+// Workouts
+//
+// Copyright 2026 Rouslan Zenetl. All Rights Reserved.
+//
+
+import AVFoundation
+import Foundation
+
+/// Shared configuration for spoken instructions. The Settings UI writes these via
+/// `@AppStorage` on the same keys, and `SpeechAnnouncer` reads them from `UserDefaults`
+/// at speak time — one source of truth, so the two never drift. Voice selection targets
+/// English, since the exercise library is authored in English regardless of the device
+/// language (a French voice reading English cues mispronounces everything).
+enum SpeechSettings {
+    // UserDefaults keys — used verbatim as the `@AppStorage` keys in Settings.
+    static let voiceIdentifierKey = "speechVoiceIdentifier"
+    static let rateKey = "speechRate"
+    static let pitchKey = "speechPitch"
+    static let volumeKey = "speechVolume"
+
+    // Defaults, shared so a missing key resolves identically in the UI and the announcer.
+    static let rateDefault = Double(AVSpeechUtteranceDefaultSpeechRate)
+    static let pitchDefault = 1.0
+    static let volumeDefault = 1.0
+
+    // Slider ranges (also used to clamp what the announcer reads).
+    static let rateRange = Double(AVSpeechUtteranceMinimumSpeechRate)...Double(AVSpeechUtteranceMaximumSpeechRate)
+    static let pitchRange = 0.5...2.0
+    static let volumeRange = 0.0...1.0
+
+    /// The exercise library is English; match voices to the content, not the device locale.
+    private static let languagePrefix = "en"
+
+    // MARK: - Current values (read by the announcer)
+
+    static var rate: Float {
+        let v = UserDefaults.standard.object(forKey: rateKey) as? Double ?? rateDefault
+        return Float(v.clamped(to: rateRange))
+    }
+
+    static var pitch: Float {
+        let v = UserDefaults.standard.object(forKey: pitchKey) as? Double ?? pitchDefault
+        return Float(v.clamped(to: pitchRange))
+    }
+
+    static var volume: Float {
+        let v = UserDefaults.standard.object(forKey: volumeKey) as? Double ?? volumeDefault
+        return Float(v.clamped(to: volumeRange))
+    }
+
+    /// The stored voice identifier, or `nil` for automatic best-available selection.
+    static var voiceIdentifier: String? {
+        let id = UserDefaults.standard.string(forKey: voiceIdentifierKey) ?? ""
+        return id.isEmpty ? nil : id
+    }
+
+    // MARK: - Voice resolution
+
+    /// The voice to speak with: the user's stored choice if it's still installed, otherwise
+    /// the best available (an enhanced/premium English voice if one is downloaded, else the
+    /// system default English voice).
+    static func resolvedVoice() -> AVSpeechSynthesisVoice? {
+        if let id = voiceIdentifier, let voice = AVSpeechSynthesisVoice(identifier: id) {
+            return voice
+        }
+        return bestAvailableVoice()
+    }
+
+    /// English voices offered in the Settings picker, best quality first.
+    static func availableVoices() -> [AVSpeechSynthesisVoice] {
+        AVSpeechSynthesisVoice.speechVoices()
+            .filter { $0.language.hasPrefix(languagePrefix) }
+            .sorted { a, b in
+                if a.quality.rank != b.quality.rank { return a.quality.rank > b.quality.rank }
+                if a.name != b.name { return a.name < b.name }
+                return a.language < b.language
+            }
+    }
+
+    /// Prefer a downloaded enhanced/premium English voice; only such an upgrade is worth
+    /// overriding the system default, which otherwise reads cues perfectly acceptably.
+    static func bestAvailableVoice() -> AVSpeechSynthesisVoice? {
+        let voices = availableVoices()
+        if let upgraded = voices.first(where: { $0.quality.rank >= AVSpeechSynthesisVoiceQuality.enhanced.rank }) {
+            return upgraded
+        }
+        let code = AVSpeechSynthesisVoice.currentLanguageCode()
+        let language = code.hasPrefix(languagePrefix) ? code : "en-US"
+        return AVSpeechSynthesisVoice(language: language) ?? voices.first
+    }
+
+    /// Human label for a voice's quality tier, shown next to its name in the picker.
+    static func qualityLabel(_ quality: AVSpeechSynthesisVoiceQuality) -> String {
+        switch quality {
+        case .premium: "Premium"
+        case .enhanced: "Enhanced"
+        case .default: "Default"
+        @unknown default: "Default"
+        }
+    }
+}
+
+private extension AVSpeechSynthesisVoiceQuality {
+    /// Orders the quality tiers for "best available" selection and picker sorting.
+    var rank: Int {
+        switch self {
+        case .premium: 3
+        case .enhanced: 2
+        case .default: 1
+        @unknown default: 0
+        }
+    }
+}
+
+private extension Double {
+    func clamped(to range: ClosedRange<Double>) -> Double {
+        min(max(self, range.lowerBound), range.upperBound)
+    }
+}