EnterChaseMode now takes (ChaseCamera, RetailChaseCamera); Active
consults CameraDiagnostics.UseRetailChaseCamera to pick which to
expose. Flag flip at runtime swaps cameras instantly (both are kept
warm). GameWindow's two EnterChaseMode call sites get a temporary
stub RetailChaseCamera; Task 7 wires proper construction +
per-frame updates.
Also folds in two minor cleanups from the Task 3 code review:
- Update() discards the unused `right` axis from BuildBasis (no
caller in the chase-cam math; viewer_offset.X is always 0)
- The three CameraDiagnostics-mutating integration tests now
save and restore the static state in try/finally to avoid
ordering-dependent contamination
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
