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/main.rs

@@ -515,6 +515,7 @@ fn input_test() -> Result<()> {
 fn parse_serve(args: &[String]) -> Result<(mgmt::Options, punktfunk1::NativeServe, bool)> {
     let mut opts = mgmt::Options::default();
     let mut native_port: u16 = 9777; // the native plane always runs now
+
     // Fixed data-plane UDP port: `Some(p)` binds p and streams direct (no hole-punch, no ~2.5 s
     // punch-timeout on a firewalled host); `None` (default) = a random port + hole-punch. Env
     // default, `--data-port` overrides.