Window Manager: Make CGS initialization delay adaptive

[malpern]

Problem

Hardcoded 2-second delay in WindowManager initialization may be insufficient for slow systems or wasteful for fast systems.

Location

App.swift

try? await Task.sleep(nanoseconds: 2_000_000_000) // 2s delay
await WindowManager.shared.initializeWithRetry()

Impact

Slow systems may fail initialization, fast systems waste 2 seconds at startup.

Fix

1. Make delay adaptive based on system responsiveness
2. Implement proper readiness check instead of fixed delay
3. Consider exponential backoff with faster initial attempts

References

• Comprehensive review: docs/code-review/comprehensive-feature-review.md section 8.3