feat(keyboard): unify assistant voice and AI workflows

Merge dictation and AI controls into one assistant surface, preserve safe insertion and clipboard actions, and align settings and tests with the new flow.

OSGKeyboardExt/Views/ClipboardKeyboardViews.swift

@@ -324,7 +324,7 @@ private struct ClipboardHistoryRow: View {
     }
 }
 
-// MARK: - Top clipboard button (replaces translation chip slot)
+// MARK: - Top clipboard button (right of the translation chip)
 
 struct KeyboardClipboardMenuButton: View, Equatable {
     @Environment(\.colorScheme) private var colorScheme
@@ -359,6 +359,7 @@ struct KeyboardClipboardMenuButton: View, Equatable {
                 .contentShape(Circle())
         }
         .buttonStyle(.plain)
+        .accessibilityIdentifier("assistant.clipboard")
         .accessibilityLabel(ExtL10n.text("keyboard.clipboard.a11y"))
         .accessibilityHint(ExtL10n.text("keyboard.clipboard.a11yHint"))
     }