Optimize chunk visibility with incremental culling updates.

[RZDESIGN]

Refresh visible batch membership only on meaningful camera/settings transitions and synchronize batch scene state directly to reduce per-frame culling and scene churn.

[RZDESIGN]

Reviewer checklist for this PR (incremental chunk culling):

• Validate camera movement across chunk boundaries: visible batches should update when crossing visibility cells; no persistent missing/ghost chunks.
• Validate view-distance toggles and value changes: scene membership should resync immediately (both enabling and disabling).
• Validate scene churn reduction: check that batch add/remove operations no longer happen every frame under stable camera position.
• Validate raycast behavior: solidMeshesInScene should stay correct with changing visibility.

Potential risk to watch closely:

• Worker stale-result guard currently checks that at least one chunk still exists; it does not fully verify batch chunk-set/version equivalence before applying results.