Write camera path to output dir if saving to the data dir fails

[krahets]

If we load data from a folder without write permissions, the Generate Command button in the render panel will not respond.

A simple solution is to write it to the output directory if writing to the data folder fails.

[kerrj]

This looks good! can you also add some sort of log statement informing users that the data dir is unwritable and that it instead wrote the path to this location?

[krahets]

Sure. Does this meet your expectations?

[krahets]

Hi @kerrj, is there any comment to be addressed?

[jb-ye]

@krahets can you also fix the linter error in core tests(Details)?

Run ruff check docs/ nerfstudio/ tests/ --output-format=github
Error: nerfstudio/viewer/render_panel.py:15:1: I001 Import block is un-sorted or un-formatted
Error: nerfstudio/viewer/render_panel.py:[11](https://github.com/nerfstudio-project/nerfstudio/actions/runs/11401455191/job/31724388520?pr=3476#step:8:12)36:29: F841 Local variable `e` is assigned to but never used
Error: Process completed with exit code 1.

[krahets]

@jb-ye Fixed