feat(editor): harden and extend FlyCamera navigation

[JeanPhilippeKernel]

Summary

• Eliminates FlyCamera yaw jitter around the zero crossing.
• Uses standard trigonometric functions instead of a low-order custom approximation, keeping angle behavior correct across Linux, macOS, and Windows.
• Keeps projection, aspect ratio, and cursor rays synchronized with docked and resized viewport extents.
• Replaces the placeholder raycast with allocation-free scene-bounds queries for adaptive movement speed, orbit pivot/collision, frame selection, and frame all.
• Adds semantic camera commands for perspective/orthographic projection, axis views, selection/all framing, and temporary numeric bookmarks.
• Adds platform-aware macOS, Windows, and Linux shortcuts, including keypad and compact-keyboard fallbacks.
• Hardens camera input ownership: text fields, popups, modals, pointer capture, and focus loss clear transient camera input; hierarchy selection no longer blocks viewport shortcuts.
• Adds focused FlyCamera, controller, scene-query, ZUI input-capture, and InputManager regression tests.

Validation

• cmake --build . --config Debug --target ZEngineTests Obelisk
• 50 focused tests pass, including MathUtils full-turn and zero-crossing coverage.

Closes #780, #781, and #782.

Related follow-up: broader deterministic coverage.
Part of the navigation roadmap and production-camera tracker.