feat(dataparser): add focus centering method

[hummat]

Summary

Add "focus" centering method from nerfstudio to sdfstudio-data dataparser for better handling of object-centric datasets.

Motivation

Upstream PRs:

• added center-method focus to sdfstudio-data autonomousvision/sdfstudio#196
• add support for "vertical" orientation and "focus" centering methods autonomousvision/sdfstudio#90

Current "poses" centering can be suboptimal for single-object datasets where cameras all look at one target. "Focus" centering computes the scene center by finding where camera rays intersect, producing better results for object-centric capture.

Usage

sdf-train neus sdfstudio-data --data ./mydata --center-method focus

Implementation Notes

• Add to sdfstudio/data/dataparsers/sdfstudio_dataparser.py
• Import centering logic from sdfstudio/cameras/camera_utils.py
• Default remains "poses" (broad compatibility)
• "focus" should only be used for object-centric datasets

Status

Not yet integrated from upstream. Note: upstream PRs also include torch._six fix which we already have.