Add "double-press to copy status" toggle + document the spoken-status changes (held for next release)

Preferences General-tab checkbox "Double-press the speak-status hotkey to copy the status to the
clipboard" (Alt+C), machine-wide (AppConfig.DoublePressStatusToCopy), on by default. When off, a
double press just reads the status again. SpeakStatusLine reads the flag only when the timing already
qualifies, so a normal single press never touches the config. Manual's speak-status section now
covers the line-by-line read, GB totals, and the double-press copy + its toggle.

Held for the next release.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/RemSound.Core/AppConfig.cs

@@ -196,6 +196,11 @@ public sealed class AppConfig
     public bool? UntickOthersWhenUsingDefaultOutput { get; set; }
     public bool? UntickOthersWhenUsingDefaultInput { get; set; }
 
+    /// <summary>If true, pressing the "speak status" global hotkey twice in quick succession copies the
+    /// status text to the clipboard (instead of just reading it again). On by default; the user can turn
+    /// it off on the Preferences General tab. Machine-wide; a screen-reader convenience (Andre's idea).</summary>
+    public bool DoublePressStatusToCopy { get; set; } = true;
+
     /// <summary>If non-null and a profile with this title exists, RemSound skips the
     /// startup profile picker and loads this profile directly. Combine with
     /// <see cref="StartMinimised"/> + the Windows auto-start registry entry