Update(procmon-plugin): Add keyboard navigation and reduce CPU sampling (#321)

* 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.

* Add keyboard navigation and reduce CPU sampling

- Panel: arrow keys move cursor, Ctrl+D kills selected, Ctrl+F focuses
  filter
- Service: sample /proc stats every 1s, ps every 2s; 2s render floor
- Widget: handle vertical bars, truncate text, use valid theme color
- Bump version to 0.4.0, plugin_api 13

procmon/plugin.toml

@@ -1,7 +1,7 @@
 id = "weinguyen/procmon"
 name = "Process Monitor"
-version = "0.3.0"
-plugin_api = 12
+version = "0.4.0"
+plugin_api = 13
 author = "weinguyen"
 license = "MIT"
 icon = "cpu"
@@ -71,6 +71,7 @@ height = 660
 placement = "floating"
 position = "center"
 open_near_click = true
+capture_keys = ["ctrl+f", "ctrl+d", "up", "down", "escape"]
 
 [[service]]
 id = "service"