clippy: clean up all warnings

Mostly `cargo clippy --fix`: needless borrows, redundant field names,
match -> if let, io::Error::other, Option::filter/map, let chains, c""
literals. By hand: drop unused impl lifetimes, a type alias for the
font preload map, Iterator::find in next_buffer, contains_key, and
allow new_ret_no_self where constructors intentionally return the
boxed/generic wrapper type.

No functional change; tests and release build unchanged.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/main.rs

@@ -159,7 +159,7 @@ fn main() {
     handle
         .insert_source(
             WaylandSource::new(event_queue).expect("Could not create WaylandSource!"),
-            |_event, queue, mut state| queue.dispatch_pending(&mut state),
+            |_event, queue, state| queue.dispatch_pending(state),
         )
         .expect("Failed to insert event source!");
 
@@ -239,23 +239,20 @@ fn main() {
             .spawn(move || {
                 let listener = UnixListener::bind(socket_path.clone()).unwrap();
                 loop {
-                    match listener.accept() {
-                        Ok((stream, _)) => {
-                            let _ = thread::Builder::new().name("ipc_client".to_string()).spawn(
-                                move || {
-                                    let r = BufReader::new(stream);
-                                    for line in r.lines() {
-                                        match line {
-                                            Ok(ref cmd) if cmd == "kill" => {
-                                                std::process::exit(0);
-                                            }
-                                            _ => {}
+                    if let Ok((stream, _)) = listener.accept() {
+                        let _ = thread::Builder::new().name("ipc_client".to_string()).spawn(
+                            move || {
+                                let r = BufReader::new(stream);
+                                for line in r.lines() {
+                                    match line {
+                                        Ok(ref cmd) if cmd == "kill" => {
+                                            std::process::exit(0);
                                         }
+                                        _ => {}
                                     }
-                                },
-                            );
-                        }
-                        _ => (),
+                                }
+                            },
+                        );
                     }
                 }
             });