Save interface-scale changes from every window

Ctrl/Cmd +/-/0 in editor and connection-manager windows called
SettingsService.persist() -> saveSettings, but only the main window's RPC
served that request: it went unanswered, the new scale applied locally, and
the next broadcast from main snapped it back.

All three window RPCs now serve saveSettings through one shared
saveSettingsHandler (persist, then hand off). index.ts's settingsSaved() is
the single place settings side effects run — transfer concurrency, locale +
app menu, the preload snapshot — whichever window saved, and it rebroadcasts
to every window EXCEPT the sender: an echo arriving behind a newer local
change (a held Cmd+) would drag it backwards. Editors are skipped by their
registry key, main and the manager by name.

Known ceiling, noted at the handler: whole-object writes, so two windows
saving in the same instant means the later one wins.

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

src/bun/editor-windows.ts

@@ -33,6 +33,8 @@ export interface EditorWindowsDeps {
 	mainFrame: () => { x: number; y: number };
 	/** Late-bound senders targeting the MAIN window's webview. */
 	notifyMain: { pathRefresh: (info: { sessionId: string; dir: string }) => void };
+	/** An editor saved settings; `key` identifies it so the rebroadcast skips it. */
+	onSettingsSaved: (settings: AppSettings, key: string) => void;
 }
 
 /**
@@ -77,6 +79,7 @@ export class EditorWindows {
 					record.suppressPrompt = true;
 					record.win?.close();
 				},
+				onSettingsSaved: (next) => this.deps.onSettingsSaved(next, key),
 			},
 		);
 
@@ -165,8 +168,11 @@ export class EditorWindows {
 		});
 	}
 
-	broadcastSettings(settings: AppSettings): void {
-		this.windows.forEach((rec) => rec.rpc.send.settingsChanged({ settings }));
+	/** `exceptKey`: the editor that saved — it already shows the new values. */
+	broadcastSettings(settings: AppSettings, exceptKey?: string): void {
+		this.windows.forEach((rec, key) => {
+			if (key !== exceptKey) rec.rpc.send.settingsChanged({ settings });
+		});
 	}
 
 	private baseTitle(ctx: EditorOpenContext): string {