style(host): cargo fmt --all (rustfmt 1.9.0 drift)

The CI image's rustfmt reformats these files (multi-line assert!/tracing! macros,
match-arm and struct-variant wrapping) — pre-existing drift that the Format job caught.
Reformat to match. Pure formatting; no logic change. main.rs also gets a blank line
before a standalone comment so rustfmt stops mis-indenting it as a trailing-comment
continuation.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/src/vdisplay/linux/kwin.rs

@@ -364,7 +364,10 @@ fn other_enabled_outputs() -> Vec<String> {
 /// then sets itself primary — the pre-group behavior). Recent kscreen marks the primary with
 /// `"priority": 1`; older builds used a `"primary": true` bool — accept either.
 fn a_managed_output_is_primary() -> bool {
-    let Ok(out) = std::process::Command::new("kscreen-doctor").arg("-j").output() else {
+    let Ok(out) = std::process::Command::new("kscreen-doctor")
+        .arg("-j")
+        .output()
+    else {
         return false;
     };
     let Ok(doc) = serde_json::from_slice::<serde_json::Value>(&out.stdout) else {