fix(mobile): eliminate >10s sidebar open delay by always mounting SessionSidebar (#1695) (#1738)

* fix(mobile): always mount SessionSidebar to eliminate >10s drawer open delay (#1695)

On mobile (Android PWA), SessionSidebar was conditionally mounted via
{mobileLeftDrawerVisible && ...}, causing the component to unmount on
drawer close and remount on every open. Each remount fired a full
data-loading cascade: paginated sessions fetch (PAGE_SIZE=500 with
retry), worktree discovery, repo status, PR status, 10+ useMemo
recomputations, and localStorage reads, manifesting as a >10s delay
before the drawer became interactive.

Desktop already avoided this by keeping SessionSidebar always mounted
inside <Sidebar> with a CSS visibility toggle.

Fix: remove the mobileLeftDrawerVisible conditional wrapper so
SessionSidebar stays mounted on mobile too, matching desktop behavior.
Visibility remains controlled by the leftDrawerX transform (off-screen
when closed). Added pointer-events-none when hidden as a defensive guard.

Added a regression test that fails if the conditional mount pattern is
reintroduced around the mobile SessionSidebar.

* fix(mobile): hide closed drawer to avoid rotation offset leak

---------

Co-authored-by: Bohdan Triapitsyn <artmore@protonmail.com>

packages/ui/src/components/layout/MainLayout.tsx

@@ -457,13 +457,30 @@ export const MainLayout: React.FC = () => {
                                     </ErrorBoundary>
                                 </div>
                             )}
-                            {mobileLeftDrawerVisible && (
+                            {/* Always mount SessionSidebar on mobile to match desktop behavior.
-                                <motion.div className="absolute inset-0 z-20 bg-sidebar" data-page-scroll-lock="true" style={{ x: leftDrawerX }} aria-hidden={!mobileLeftDrawerOpen}>
+                                Conditional mount (mobileLeftDrawerVisible && ...) caused a
-                                    <ErrorBoundary>
+                                data-loading cascade on every drawer open: paginated sessions
-                                        <SessionSidebar mobileVariant />
+                                fetch, worktree discovery, repo status, PR status, and 10+ memo
-                                    </ErrorBoundary>
+                                recomputations. On Android PWA this manifested as a >10s delay
-                                </motion.div>
+                                before the drawer became interactive (issue #1695). Visibility is
-                            )}
+                                controlled by the leftDrawerX transform (off-screen when closed).
+                                The invisible class matters when fully hidden: leftDrawerWidth is
+                                not recomputed on resize/rotation, so a closed drawer translated by
+                                the old width could otherwise peek into the viewport; it also keeps
+                                the off-screen sidebar out of the tab order and skips painting it. */}
+                            <motion.div
+                                className={cn(
+                                    'absolute inset-0 z-20 bg-sidebar',
+                                    !mobileLeftDrawerVisible && 'pointer-events-none invisible',
+                                )}
+                                data-page-scroll-lock="true"
+                                style={{ x: leftDrawerX }}
+                                aria-hidden={!mobileLeftDrawerOpen}
+                            >
+                                <ErrorBoundary>
+                                    <SessionSidebar mobileVariant />
+                                </ErrorBoundary>
+                            </motion.div>
                             {mobileRightDrawerVisible && (
                                 <motion.div className="absolute inset-0 z-20 bg-sidebar" data-page-scroll-lock="true" style={{ x: rightDrawerX }} aria-hidden={!mobileRightSidebarOpen}>
                                     <ErrorBoundary>

packages/ui/src/components/layout/__tests__/mainLayoutMobileSidebarMount.test.ts

@@ -0,0 +1,35 @@
+import { describe, expect, test } from 'bun:test';
+import { readFileSync } from 'node:fs';
+import { dirname, join } from 'node:path';
+import { fileURLToPath } from 'node:url';
+
+const __dirname = dirname(fileURLToPath(import.meta.url));
+const mainLayoutSource = readFileSync(
+    join(__dirname, '..', 'MainLayout.tsx'),
+    'utf-8',
+);
+
+describe('MainLayout mobile SessionSidebar mount (issue #1695 regression guard)', () => {
+    test('mobile SessionSidebar is not conditionally mounted on mobileLeftDrawerVisible', () => {
+        const mobileSidebarIndex = mainLayoutSource.indexOf('<SessionSidebar mobileVariant');
+        expect(mobileSidebarIndex).toBeGreaterThan(-1);
+
+        const windowStart = Math.max(0, mobileSidebarIndex - 400);
+        const precedingWindow = mainLayoutSource.slice(windowStart, mobileSidebarIndex);
+
+        expect(/\{\s*mobileLeftDrawerVisible\s*&&\s*\(/.test(precedingWindow)).toBe(false);
+
+        expect(precedingWindow.includes('pointer-events-none')).toBe(true);
+    });
+
+    test('desktop SessionSidebar is rendered inside Sidebar without drawer-visibility gating', () => {
+        const desktopSidebarIndex = mainLayoutSource.indexOf('<SessionSidebar />');
+        expect(desktopSidebarIndex).toBeGreaterThan(-1);
+
+        const windowStart = Math.max(0, desktopSidebarIndex - 300);
+        const precedingWindow = mainLayoutSource.slice(windowStart, desktopSidebarIndex);
+
+        expect(precedingWindow).toContain('<Sidebar');
+        expect(/mobileLeftDrawerVisible\s*&&/.test(precedingWindow)).toBe(false);
+    });
+});