Watch: show version/build on screen, surface recording errors in UI

A tester on real hardware has no console, so a failed start looked like
a dead button and there was no way to tell which build the watch had
actually installed. Show the stamped version/build under the record
button, display the last start error in place of the hint text, and
fall back to the default audio session mode if .spokenAudio is rejected
with the .record category.

Claude-Session: https://claude.ai/code/session_01GKfAiKiQKLDTmbiGva4FGE

Notes Watch App/Views/RecordView.swift

@@ -17,6 +17,12 @@ struct RecordView: View {
                     Text(Self.elapsedString(recorder.elapsed))
                         .font(.system(.title3, design: .rounded).monospacedDigit())
                         .foregroundStyle(.secondary)
+                } else if let error = services.lastError {
+                    Text(error)
+                        .font(.caption2)
+                        .foregroundStyle(.red)
+                        .multilineTextAlignment(.center)
+                        .lineLimit(3)
                 } else {
                     Text("Tap to record")
                         .font(.footnote)
@@ -24,6 +30,7 @@ struct RecordView: View {
                 }
                 pendingFooter
             }
+            buildFooter
         }
         .padding()
         .containerBackground(.red.gradient, for: .navigation)
@@ -76,6 +83,16 @@ struct RecordView: View {
         }
     }
 
+    /// Version + build stamped by update_build_number.sh, so a tester can tell
+    /// at a glance which build the watch actually installed.
+    private var buildFooter: some View {
+        let version = Bundle.main.object(forInfoDictionaryKey: "CFBundleShortVersionString") as? String ?? "?"
+        let build = Bundle.main.object(forInfoDictionaryKey: "CFBundleVersion") as? String ?? "?"
+        return Text("v\(version) (\(build))")
+            .font(.system(size: 10))
+            .foregroundStyle(.tertiary)
+    }
+
     /// mm:ss for the elapsed readout.
     static func elapsedString(_ interval: TimeInterval) -> String {
         let total = Int(interval)