Accumulate OpenCode settings restarts behind Apply & Restart

Defer OpenCode reloads after settings mutations, track pending changes,
and expose a top-right Apply & Restart OpenCode action with a counter so
sessions stay available until the user explicitly applies.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/lib/opencode/deferredRestart.test.ts

@@ -0,0 +1,62 @@
+import { describe, expect, mock, test } from 'bun:test';
+
+describe('deferred OpenCode restart helpers', () => {
+  test('isDeferredRestartPayload detects deferred responses', async () => {
+    const { isDeferredRestartPayload } = await import('./deferredRestart');
+
+    expect(isDeferredRestartPayload({
+      requiresReload: false,
+      requiresRestart: true,
+      restartDeferred: true,
+    })).toBe(true);
+
+    expect(isDeferredRestartPayload({
+      requiresReload: false,
+      requiresRestart: true,
+    })).toBe(true);
+
+    expect(isDeferredRestartPayload({
+      requiresReload: true,
+      message: 'reloading',
+    })).toBe(false);
+
+    expect(isDeferredRestartPayload({
+      requiresManualRestart: true,
+      requiresRestart: true,
+      restartDeferred: true,
+    })).toBe(false);
+  });
+
+  test('noteDeferredRestartFromPayload records pending changes', async () => {
+    const { usePendingOpenCodeRestartStore } = await import('@/stores/usePendingOpenCodeRestartStore');
+    usePendingOpenCodeRestartStore.getState().clear();
+
+    const { noteDeferredRestartFromPayload } = await import('./deferredRestart');
+    const noted = noteDeferredRestartFromPayload({
+      requiresReload: false,
+      requiresRestart: true,
+      restartDeferred: true,
+    }, 'mcp', { id: 'filesystem' });
+
+    expect(noted).toBe(true);
+    expect(usePendingOpenCodeRestartStore.getState().changes).toHaveLength(1);
+    expect(usePendingOpenCodeRestartStore.getState().changes[0]?.scope).toBe('mcp');
+  });
+
+  test('applyPendingOpenCodeRestart clears pending changes after success', async () => {
+    mock.module('@/stores/useAgentsStore', () => ({
+      reloadOpenCodeConfiguration: async () => undefined,
+    }));
+
+    const { usePendingOpenCodeRestartStore } = await import('@/stores/usePendingOpenCodeRestartStore');
+    usePendingOpenCodeRestartStore.getState().clear();
+    usePendingOpenCodeRestartStore.getState().recordChange({ scope: 'agents', id: 'demo' });
+
+    const { applyPendingOpenCodeRestart } = await import('./deferredRestart');
+    const result = await applyPendingOpenCodeRestart({ message: 'Applying…' });
+
+    expect(result).toEqual({ ok: true });
+    expect(usePendingOpenCodeRestartStore.getState().changes).toHaveLength(0);
+    expect(usePendingOpenCodeRestartStore.getState().isApplying).toBe(false);
+  });
+});