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/widgets/calendar.rs

@@ -69,7 +69,7 @@ impl Calendar {
     fn draw_month(
         &mut self,
         fonts: &mut FontMap,
-        mut view: &mut BufferView,
+        view: &mut BufferView,
         orig: NaiveDate,
         mut time: NaiveDate,
     ) {
@@ -100,7 +100,7 @@ impl Calendar {
                             + (self.size * DAY_FACTOR * 0.2).ceil() as u32,
                     )),
                     c,
-                    &wk_chr,
+                    wk_chr,
                 )
                 .unwrap();
         }
@@ -124,9 +124,7 @@ impl Calendar {
             12 => "December",
             _ => panic!("impossible value"),
         };
-        month_font
-            .draw_text(&mut view, Color::WHITE, month_str)
-            .unwrap();
+        month_font.draw_text(view, Color::WHITE, month_str).unwrap();
 
         //
         // Draw the year
@@ -199,7 +197,7 @@ impl Calendar {
     }
 }
 
-impl<'a> Widget for Calendar {
+impl Widget for Calendar {
     fn get_dirty(&self) -> bool {
         self.dirty
     }
@@ -209,11 +207,8 @@ impl<'a> Widget for Calendar {
     }
 
     fn event(&mut self, event: &Event) {
-        match event {
-            Event::NewMinute => {
-                self.dirty = true;
-            }
-            _ => (),
+        if let Event::NewMinute = event {
+            self.dirty = true;
         }
     }
 
@@ -299,9 +294,8 @@ impl<'a> Widget for Calendar {
         self.geometry = Geometry {
             x: geometry.x,
             y: geometry.y,
-            width: cal_width * self.shown_sections_x as u32
-                + cal_pad * (self.shown_sections_x as u32 - 1),
-            height: cal_height * self.shown_sections_y as u32,
+            width: cal_width * self.shown_sections_x + cal_pad * (self.shown_sections_x - 1),
+            height: cal_height * self.shown_sections_y,
         };
         self.geometry
     }
@@ -344,8 +338,8 @@ impl<'a> Widget for Calendar {
         Geometry {
             x: 0,
             y: 0,
-            width: width,
-            height: height,
+            width,
+            height,
         }
     }
 }