Own printers, driverless only

The fourth panel this desktop handed to GNOME Settings, and the last one
worth owning.

Driverless only, deliberately. Adding a printer that describes its own
capabilities over IPP is supported; choosing a PPD or fetching a vendor
driver is not, and the page says so rather than pretending. That
restraint is the whole design: a wrong driver produces a printer that
accepts jobs, reports success, and prints nothing, which is the worst
failure this page could ship because it looks like it worked. A printer
old enough to need a PPD stays a job for the system printer tool.

Printers and the queue are separate cards because they answer separate
questions. Which printers exist is one; where a document went is the
other, and it is the one that actually brings someone here -- so the
queue is a single list across every printer.

Device URIs are validated by scheme before reaching CUPS, whose backends
run as root. file: and pipe: do not lead to a printer and are refused
here rather than further down.

This machine has no printer, so the page was built against a temporary
CUPS queue that was created, exercised through the service, and removed;
the service was confirmed to observe the removal rather than merely
perform it. Discovery and the driverless add path are verified by their
refusals rather than against hardware.

Claude-Session: https://claude.ai/code/session_01BRvzt4H8XXLPVH5MyYdk9L

config/dot/quickshell/modules/settings/SettingsSidebar.qml

@@ -27,6 +27,7 @@ Rectangle {
         { page: "displays", label: "Displays", icon: "\u{F0379}" },
         { page: "connectivity", label: "Network & Devices", icon: "\u{F08D4}" },
         { page: "sharing", label: "Sharing", icon: "\u{F04E6}" },
+        { page: "printers", label: "Printers", icon: "\u{F042A}" },
         { page: "home-phone", label: "Home & Phone", icon: "\u{F02DC}" },
         { page: "desktop", label: "Desktop & Dock", icon: "\u{F04A4}" },
         { page: "sound", label: "Sound", icon: "\u{F057E}" },