fix: don't let kitty graphics detection crash IPython startup

_supports_kitty_graphics() walks the process tree with psutil at import
time to detect a graphics-capable terminal. On shared multi-user systems
where /proc is mounted with hidepid (common on HPC clusters), reaching an
ancestor process owned by another user raises psutil.AccessDenied, which
was unhandled and aborted the entire `import IPython`.

Catch psutil/OS errors during the walk and treat them as "graphics
unsupported" instead. A real supported terminal is one of the user's own
near ancestors and is found before any restricted PID, so detection
capability is unchanged.