fix(message): use unicode char count for text width

src/commit/types/commit_type.rs

@@ -61,6 +61,15 @@ impl CommitType {
             Self::Revert => "revert",
         }
     }
+
+    /// Returns the length in characters
+    ///
+    /// `is_empty()` is intentionally absent: `CommitType` is
+    /// guaranteed non-empty, so the concept does not apply.
+    #[allow(clippy::len_without_is_empty)]
+    pub fn len(&self) -> usize {
+        self.as_str().chars().count()
+    }
 }
 
 impl std::fmt::Display for CommitType {

src/commit/types/description.rs

@@ -39,7 +39,7 @@ impl Description {
     /// non-empty by its constructor, so the concept does not apply.
     #[allow(clippy::len_without_is_empty)]
     pub fn len(&self) -> usize {
-        self.0.len()
+        self.0.chars().count()
     }
 }
 

src/commit/types/message.rs

@@ -70,13 +70,10 @@ impl ConventionalCommit {
     /// - Without scope: `len(type) + 2 + len(description)`
     ///   (the 2 accounts for colon and space: ": ")
     pub fn first_line_len(&self) -> usize {
-        if self.scope.is_empty() {
-            // type: description
-            self.commit_type.as_str().len() + 2 + self.description.len()
-        } else {
-            // type(scope): description
-            self.commit_type.as_str().len() + self.scope.as_str().len() + 4 + self.description.len()
-        }
+        self.commit_type.len()
+            + self.scope.header_segment_len()
+            + 2 // ": "
+            + self.description.len()
     }
 
     /// Format the complete commit messsage

src/commit/types/scope.rs

@@ -25,8 +25,13 @@ impl Scope {
             });
         }
         match lazy_regex::regex_find!(r"[^-a-zA-Z0-9_/]", &value) {
-            Some(val) => Err(ScopeError::InvalidCharacter(val.chars().next().unwrap())),
             None => Ok(Self(value)),
+            Some(val) => val
+                .chars()
+                .next()
+                .map(ScopeError::InvalidCharacter)
+                .map(Err)
+                .unwrap_or_else(|| unreachable!("regex match is always non-empty")),
         }
     }
 
@@ -44,6 +49,16 @@ impl Scope {
     pub fn as_str(&self) -> &str {
         self.0.as_str()
     }
+
+    /// Returns itself as a formatted header segment
+    pub fn header_segment(&self) -> String {
+        format!("({self})")
+    }
+
+    /// Returns the visible length of the header segment
+    pub fn header_segment_len(&self) -> usize {
+        self.header_segment().chars().count()
+    }
 }
 
 impl std::fmt::Display for Scope {