* Add procmon plugin with live process panel
New Noctalia plugin: bar widget shows CPU/RAM usage and process
count; floating panel has a sortable, searchable process table
with per-process kill. Background service samples ps and /proc
stats and publishes via plugin state.
* Throttle data-driven panel renders
Rebuild table at most every 500ms to stay within the panel update
CPU budget. User interactions still render immediately; only state
watches and the tick go through maybeRender().
* Update procmon deps and fix timestamp precision
Document head, grep, and cat as required commands. Correct refresh
interval default to 1000 ms. Sample refreshedAtMs in milliseconds.
