6.4: Navigation And View Control UX Pass

[kmeirlaen]

Included survey bullets:

• Navigation feels clunky.
• Add game-engine navigation parity.
• Include Q/E for up/down and more precise mouse behavior.
• Add start-position anchor for larger splats.
• Realign base orientation.

Suggested solution:

Treat navigation as part of production usability, not a cosmetic preference. Add missing conventional controls, make bindings discoverable, and provide saved navigation anchors.

Actionable scope:

• Review and adjust default navigation bindings.
• Add Q/E up/down if compatible with existing bindings.
• Add start-position anchor.
• Add "return to start" or "set start view."
• Link base orientation work with Epic 2.

Acceptance signal:

• Users familiar with DCC/game-engine navigation can move through large splats without fighting the viewport.

Dependencies:

• Input system.
• Camera controller.
• View state serialization.