fix: add VUScale.spokenLevel with proper clamping and non-finite handling

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Sources/SstUI/Instruments.swift

@@ -20,6 +20,14 @@ public enum VUScale {
     public static func angle(forFraction fraction: Double) -> Double {
         (-MeterTokens.vuArcDegrees / 2 + MeterTokens.vuArcDegrees * fraction) * .pi / 180
     }
+
+    /// Level as VoiceOver should say it: rounded to steps of 3 VU, clamped to the scale, "stil" for non-finite input.
+    public static func spokenLevel(fromDbfs dbfs: Double) -> String {
+        guard dbfs.isFinite else { return "stil" }
+        let stepped = (vu(fromDbfs: dbfs) / 3).rounded() * 3
+        let clamped = min(MeterTokens.vuMax, max(MeterTokens.vuMin, stepped))
+        return "\(Int(clamped)) VU"
+    }
 }
 
 /// Second-order needle: reaches ~99 % in `response` seconds, slight overshoot for damping < 1.

Sources/SstUI/VUMeterView.swift

@@ -60,8 +60,7 @@ public struct VUMeterView: View {
     /// Rounded to steps of 3 VU so VoiceOver is not flooded with changes.
     private var spokenValue: String {
         guard isActive else { return "stil" }
-        let vu = (VUScale.vu(fromDbfs: levelDbfs) / 3).rounded() * 3
-        return "\(Int(vu)) VU"
+        return VUScale.spokenLevel(fromDbfs: levelDbfs)
     }
 
     // MARK: drawing (design coordinates: MeterTokens.vuWidth × vuHeight)

Tests/SstUITests/InstrumentsTests.swift

@@ -106,3 +106,26 @@ struct LEDBarTests {
         #expect(LEDBar.litCount(forFraction: -1) == 0)
     }
 }
+
+struct SpokenLevelTests {
+    @Test func nonFiniteInputReturnsStil() {
+        #expect(VUScale.spokenLevel(fromDbfs: -.infinity) == "stil")
+        #expect(VUScale.spokenLevel(fromDbfs: .nan) == "stil")
+    }
+
+    @Test func referenceLevel() {
+        #expect(VUScale.spokenLevel(fromDbfs: -20) == "0 VU")
+    }
+
+    @Test func negativeLevel() {
+        #expect(VUScale.spokenLevel(fromDbfs: -30) == "-9 VU")
+    }
+
+    @Test func clampedToMinimum() {
+        #expect(VUScale.spokenLevel(fromDbfs: -120) == "-20 VU")
+    }
+
+    @Test func clampedToMaximum() {
+        #expect(VUScale.spokenLevel(fromDbfs: 10) == "3 VU")
+    }
+}