chore: clear clippy warnings and refresh the GUI README

`cargo clippy --fix`: drop needless borrows in interactive.rs, remove an
unneeded `return`, and derive `Default` for `HostState` / the config struct
instead of hand-writing it. No behaviour change.

README: the GUI host screen now lists connected viewers with a Kick button
and notifies on join/leave — update the description, which still mentioned
only a "live viewer count".

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/gui/mod.rs

@@ -165,6 +165,7 @@ impl PlayerSel {
 
 /// Host-screen state: the config form fields plus, once started, the running
 /// child and the latest values parsed from its event stream.
+#[derive(Default)]
 struct HostState {
     // form
     quality: QualitySel,
@@ -190,27 +191,6 @@ struct HostState {
     viewers: Vec<String>,
 }
 
-impl Default for HostState {
-    fn default() -> Self {
-        Self {
-            quality: QualitySel::default(),
-            max_viewers: 0,
-            no_hwencode: false,
-            window: false,
-            proc: None,
-            ticket: None,
-            info: None,
-            active: 0,
-            max: 0,
-            capturing: false,
-            copied: false,
-            last_refusal: None,
-            error: None,
-            viewers: Vec::new(),
-        }
-    }
-}
-
 /// The host config summary echoed back by the child's `host_info` event.
 struct HostInfo {
     display: String,