feat(host): list-monitors CLI, and two bugs it caught on-glass

An operator configuring an unattended host has to learn the connector
names from somewhere, and "curl the management API before the host is
configured" is not it. `punktfunk-host list-monitors` prints them with
geometry and flags the pinned one.

Running it under a real sway immediately caught two defects the unit tests
could not:

  - the query used the `swaymsg` command helper, which inserts `--`, so
    `-t get_outputs` came back as "Unknown/invalid command '-t'". Queries
    now go through a `swaymsg_query` helper that cannot make that mistake.
  - compositors write the literal "Unknown" rather than leaving make/model
    empty, so the picker label read "Unknown Unknown". One `describe`
    helper now treats that as absent, for all four backends.

Verified on a headless two-output sway: names, modes, positions, scale and
the case-insensitive pin all resolve.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/pf-vdisplay/src/vdisplay/linux/mutter.rs

@@ -840,14 +840,9 @@ pub(crate) fn list_monitors() -> Result<Vec<crate::monitors::PhysicalMonitor>> {
             let (w, h, refresh) = current_mode_full(&state, connector)
                 .map(|(_id, w, h, hz)| (w.max(0) as u32, h.max(0) as u32, (hz * 1000.0) as u32))
                 .unwrap_or((0, 0, 0));
-            let label = format!("{vendor} {product}");
             crate::monitors::PhysicalMonitor {
                 connector: connector.clone(),
-                description: if label.trim().is_empty() {
-                    connector.clone()
-                } else {
-                    label.trim().to_string()
-                },
+                description: crate::monitors::describe(vendor, product, connector),
                 width: w,
                 height: h,
                 refresh_mhz: refresh,