Spawn shell subprocesses with bash -c instead of bash -lc

Each `bash -lc` starts a login shell that re-sources the profile
(mise activation, /etc/profile.d) on every invocation — ~16 forks per
call versus ~2 for `bash -c` — which taxes every menu/panel/launcher
action the shell shells out for. The session already exports PATH and
env to the shell, so omarchy commands resolve fine under `bash -c`.

Switch the internal/omarchy-owned spawns (theme+background switches,
brightness, monitor scaling, DNS, lock/fingerprint, keyboard-layout
probe, voxtype status, and the `:`/printf state-file writes) to
`bash -c`. Leave `bash -lc` on the sites that run user-configurable
commands (custom bar-widget exec, menu provider/guard scripts,
launcher scan commands, configurable idle/screensaver command), where
a user's command may rely on their login environment.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

shell/plugins/menu/Menu.qml

@@ -115,9 +115,9 @@ Item {
     root.doneFile = ""
 
     if (selection === null || selection === undefined) {
-      resultProc.command = ["bash", "-lc", ": > " + Util.shellQuote(activeDoneFile)]
+      resultProc.command = ["bash", "-c", ": > " + Util.shellQuote(activeDoneFile)]
     } else {
-      resultProc.command = ["bash", "-lc", "printf '%s\\n' " + Util.shellQuote(selection) + " > " + Util.shellQuote(activeSelectionFile) + "; : > " + Util.shellQuote(activeDoneFile)]
+      resultProc.command = ["bash", "-c", "printf '%s\\n' " + Util.shellQuote(selection) + " > " + Util.shellQuote(activeSelectionFile) + "; : > " + Util.shellQuote(activeDoneFile)]
     }
     resultProc.running = true
   }