feat(desktop): consolidate declarative workstation profile

Capture desktop-specific system, session, Noctalia, and Pi integration alongside shared laptop support. Retire obsolete X11 configuration and make package ownership explicit for repeatable Decman deployments.

.gitignore

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+# Home-directory targets owned by system-config/Decman.
+.config/alacritty/
+.config/environment.d/pi-status-bridge.conf
+.config/fish/config.fish
+.config/hypr/
+.config/kitty/
+.config/mimeapps.list
+.config/noctalia/
+.config/systemd/user/idle-inhibitor-monitor.service
+.config/systemd/user/pi-status-bridge.service
+.config/systemd/user/ssh-agent.service
+.config/user-dirs.dirs
+.config/yazi/
+.local/bin/idle-inhibitor-monitor
+.local/bin/pi-status-ui
+.local/bin/wayshell-blanker
+.local/share/noctalia/plugins/knowledge-lookup/
+.local/share/noctalia/plugins/pi-status-bridge/
+.local/share/noctalia/plugins/system-status/