Count-based dirty tracking missed content changes when tile/visibility
count stayed the same (e.g., door opening, player moving through
corridor). Now re-renders all layers when GameState.current_tick
advances, which correctly handles every snapshot change.
Adds 3 tests for tick advancement and same-count-different-content
scenarios. 68 total tests, 0 failures.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>