fix(desktop): keep statusctl quiet when the mode file is absent

read_mode() failed on a missing mode file with a shell redirection
error, 'statusctl: line 56: .../status.dnd: No such file or directory',
printed to stderr on every get/toggle before the file existed and
polluting waybar's exec stderr.

The '2>/dev/null' sat on the 'tr' command, but the error is the parent
shell's input redirection failure, which that redirect cannot suppress.
Guard on '[[ -e "$file" ]]' before reading; a missing file still
reads as 0, which was always the contract.

Mirror the fix into the plan so plan and script agree.

0 files changed, 0 insertions, 0 deletions