* feat: add gamer-mode plugin
Live CPU, RAM, swap, GPU, VRAM, load and network readings in the bar and a
panel, plus a one-click mode that suspends background resource hogs and
restores exactly what it suspended.
* chore: rebuild the thumbnail with the upstream generator
Produced by assets.noctalia.dev/plugins/thumbnail-generator.html with the
title, the Gaming tag, the panel screenshot and the Red accent, rather than
composed by hand at the same dimensions.
* fix(gamer-mode): write the session before suspending anything
Enable suspended targets first and dropped the writeSnapshot return, so
a failed write left processes frozen and units stopped with no record to
restore them from, while the service published gamer mode as off and
switched the power profile.
The snapshot now lands on disk first, and a failed write aborts the
enable with the machine untouched and an error notification.
Writing first can record a target whose suspend command then failed.
That direction is safe: thawing is unconditional and SIGCONT to a
running process is a no-op, and a stop target restarts only after a live
probe says it is still down.
