Mode Switch Test: Pixel Base
1. Pixel -> DOM (pushState)
2. Pixel -> DOM (replaceState)
3. Back / Forward (soft traversal)
4. Rapid same-direction: Pixel -> DOM x3
5. Rapid mixed: Pixel->DOM->Pixel->DOM
6. Hash change (no mode switch, clears pending)
7. Same-mode nav cancels pending hint
8. Forward after back
9. replaceState on nav URL
Log: