style: apply rustfmt to proto.rs

Fixes CI fmt check failure — rustfmt wants multi-line assert_eq! for
long struct literals and the varint roundtrip assertion.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/ericrfb/src/proto.rs

@@ -135,15 +135,11 @@ fn decode_modified_utf8(data: &[u8]) -> Result<String> {
             // Two-byte sequence: 110xxxxx 10xxxxxx
             12 | 13 => {
                 if i + 1 >= data.len() {
-                    return Err(ProtoError::InvalidUtf8(
+                    return Err(ProtoError::InvalidUtf8("truncated 2-byte sequence".into()));
-                        "truncated 2-byte sequence".into(),
-                    ));
                 }
                 let b2 = data[i + 1];
                 if b2 & 0xC0 != 0x80 {
-                    return Err(ProtoError::InvalidUtf8(
+                    return Err(ProtoError::InvalidUtf8("invalid continuation byte".into()));
-                        "invalid continuation byte".into(),
-                    ));
                 }
                 let cp = ((b as u32 & 0x1F) << 6) | (b2 as u32 & 0x3F);
                 out.push(char::from_u32(cp).unwrap_or('\u{FFFD}'));
@@ -152,19 +148,14 @@ fn decode_modified_utf8(data: &[u8]) -> Result<String> {
             // Three-byte sequence: 1110xxxx 10xxxxxx 10xxxxxx
             14 => {
                 if i + 2 >= data.len() {
-                    return Err(ProtoError::InvalidUtf8(
+                    return Err(ProtoError::InvalidUtf8("truncated 3-byte sequence".into()));
-                        "truncated 3-byte sequence".into(),
-                    ));
                 }
                 let b2 = data[i + 1];
                 let b3 = data[i + 2];
                 if (b2 & 0xC0 != 0x80) || (b3 & 0xC0 != 0x80) {
-                    return Err(ProtoError::InvalidUtf8(
+                    return Err(ProtoError::InvalidUtf8("invalid continuation byte".into()));
-                        "invalid continuation byte".into(),
-                    ));
                 }
-                let cp =
+                let cp = ((b as u32 & 0x0F) << 12) | ((b2 as u32 & 0x3F) << 6) | (b3 as u32 & 0x3F);
-                    ((b as u32 & 0x0F) << 12) | ((b2 as u32 & 0x3F) << 6) | (b3 as u32 & 0x3F);
                 out.push(char::from_u32(cp).unwrap_or('\u{FFFD}'));
                 i += 3;
             }
@@ -340,7 +331,11 @@ mod tests {
             let mut buf = Vec::new();
             write_varint(&mut buf, val).unwrap();
             let mut c = Cursor::new(&buf);
-            assert_eq!(read_varint(&mut c).unwrap(), val, "roundtrip failed for {val}");
+            assert_eq!(
+                read_varint(&mut c).unwrap(),
+                val,
+                "roundtrip failed for {val}"
+            );
         }
     }
 
@@ -384,7 +379,16 @@ mod tests {
 
         let mut c = Cursor::new(&data[..]);
         let hdr = RectHeader::read_from(&mut c).unwrap();
-        assert_eq!(hdr, RectHeader { x: 10, y: 20, w: 640, h: 480, encoding: 7 });
+        assert_eq!(
+            hdr,
+            RectHeader {
+                x: 10,
+                y: 20,
+                w: 640,
+                h: 480,
+                encoding: 7
+            }
+        );
     }
 
     #[test]