refactor(tabs): consolidate [+] button with app-switcher sidebar

The tab bar [+] button now opens the same sidebar as the header's
rApp dropdown instead of its own duplicate menu. Reduces UI clutter
and gives one consistent place to browse/add rApps.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/components/rstack-app-switcher.ts

@@ -557,6 +557,12 @@ export class RStackAppSwitcher extends HTMLElement {
 		this.#render();
 	}
 
+	/** Open the sidebar programmatically (used by tab bar [+] button) */
+	open() {
+		this.#isOpen = true;
+		this.#render();
+	}
+
 	#getSpaceSlug(): string {
 		// Read from the space switcher or URL
 		const spaceSwitcher = document.querySelector("rstack-space-switcher");

shared/components/rstack-tab-bar.ts

@@ -1085,16 +1085,18 @@ export class RStackTabBar extends HTMLElement {
 			});
 		});
 
-		// Add button — click + touch support
+		// Add button — open the header's app-switcher sidebar
 		const addBtn = this.#shadow.getElementById("add-btn");
-		const toggleAddMenu = (e: Event) => {
+		const openAppSwitcher = (e: Event) => {
 			e.stopPropagation();
 			e.preventDefault();
-			this.#addMenuOpen = !this.#addMenuOpen;
-			this.#render();
+			const switcher = document.querySelector("rstack-app-switcher") as any;
+			if (switcher?.open) {
+				switcher.open();
+			}
 		};
-		addBtn?.addEventListener("click", toggleAddMenu);
-		addBtn?.addEventListener("touchend", toggleAddMenu);
+		addBtn?.addEventListener("click", openAppSwitcher);
+		addBtn?.addEventListener("touchend", openAppSwitcher);
 
 		// Add menu items — click + touch support
 		this.#shadow.querySelectorAll<HTMLElement>(".add-menu-item").forEach(item => {