Add the announcement of switched workspaces from Niri.

I haven't tested this with Braille support; I don't remember what I did with the cable.

internal/app/event_state.go

@@ -97,6 +97,9 @@ type eventPresentationState struct {
 	lastSound           string
 	lastLiveText        string
 	lastLiveAt          time.Time
+	lastAnnouncement    string
+	lastAnnouncementBus string
+	lastAnnouncementAt  time.Time
 	comboHistory        comboPresentation
 	echoPreview         echoPreviewPresentation
 	// Retain this identity after the history window closes so delayed GTK
@@ -166,6 +169,7 @@ func (state *eventLoopState) clearObjectFocus(brailleOutput brailleFrameEnqueuer
 	state.focusCaretID, state.focusCaretSequence = atspi.ObjectID{}, 0
 	state.lastSpokenPath, state.lastSpokenText, state.lastSound = "", "", ""
 	state.lastLiveText, state.lastLiveAt = "", time.Time{}
+	state.lastAnnouncement, state.lastAnnouncementBus, state.lastAnnouncementAt = "", "", time.Time{}
 	state.comboHistory = comboPresentation{}
 	state.echoPreview = echoPreviewPresentation{}
 	state.typingPath, state.typingText, state.suppressNextCaretPath = "", "", ""