Tile windowing system

stores/windowStore.ts

@@ -0,0 +1,42 @@
+"use client";
+
+import { useSyncExternalStore } from "react";
+import { PanelId } from "@/app/components/windows/types";
+
+// ── State ─────────────────────────────────────────────────────────────────────
+
+interface WindowFocus {
+	paneId: string | null;
+	panelId: PanelId | null;
+}
+
+let focus: WindowFocus = { paneId: null, panelId: null };
+const focusListeners = new Set<() => void>();
+const INITIAL_FOCUS: WindowFocus = { paneId: null, panelId: null };
+
+export function setFocusedContext(paneId: string, panelId: PanelId) {
+	focus = { paneId, panelId };
+	focusListeners.forEach((l) => l());
+}
+
+export function useFocusedWindowState(): WindowFocus {
+	return useSyncExternalStore(
+		(cb) => { focusListeners.add(cb); return () => focusListeners.delete(cb); },
+		() => focus,
+		() => INITIAL_FOCUS,
+	);
+}
+
+// ── View change requests (sidebar → focused pane) ─────────────────────────────
+
+type ViewChangeListener = (panelId: PanelId) => void;
+const viewChangeListeners = new Set<ViewChangeListener>();
+
+export function requestViewChange(panelId: PanelId) {
+	viewChangeListeners.forEach((l) => l(panelId));
+}
+
+export function subscribeViewChange(fn: ViewChangeListener): () => void {
+	viewChangeListeners.add(fn);
+	return () => { viewChangeListeners.delete(fn); };
+}