feat: enhance Asian character detection per iblea's suggestion

Improved Unicode width calculation for Korean and Japanese characters
by adding dedicated checkAsianCharacter helper function.

Changes:
- Add checkAsianCharacter() with comprehensive Korean/Japanese ranges:
  * Korean Hangul (unicode.Hangul)
  * Korean Hangul Jamo (0x1100-0x11FF)
  * Korean Hangul Compatibility Jamo (0x3130-0x318F)
  * Enclosed CJK Letters (0x3200-0x32FF)
  * Japanese Hiragana (unicode.Hiragana)
  * Japanese Katakana (unicode.Katakana)

- Add Miscellaneous Technical emoji range (0x2300-0x23FF) for clock
  symbols and similar emoji

- Add comprehensive tests for Korean/Japanese character detection
- Add TestCheckAsianCharacter for validating the helper function

Credit: Implementation based on iblea's code review suggestion
on PR charmbracelet#563

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: kolkov

size.go

@@ -60,6 +60,20 @@ func stringWidth(s string) int {
 	return ansiWidth
 }
 
+// checkAsianCharacter checks if the character is an Asian character (character of 2 width)
+func checkAsianCharacter(r rune) bool {
+	if unicode.Is(unicode.Han, r) || // CJK characters
+		unicode.Is(unicode.Hangul, r) || // Korean Hangul characters
+		(r >= 0x3130 && r <= 0x318F) || // Hangul Compatibility Jamo (ㄱ-ㅎ, ㅏ-ㅣ)
+		(r >= 0x1100 && r <= 0x11FF) || // Korean Hangul Jamo (ㄱ-ㅎ, ㅏ-ㅣ)
+		(r >= 0x3200 && r <= 0x32FF) || // Enclosed CJK Letters and Months
+		unicode.Is(unicode.Hiragana, r) || // Japanese Hiragana characters
+		unicode.Is(unicode.Katakana, r) { // Japanese Katakana characters
+		return true
+	}
+	return false
+}
+
 // containsComplexUnicode checks if string contains emoji or complex Unicode
 func containsComplexUnicode(s string) bool {
 	for _, r := range s {
@@ -68,10 +82,10 @@ func containsComplexUnicode(s string) bool {
 		   (r >= 0x1F300 && r <= 0x1F5FF) || // Misc Symbols and Pictographs
 		   (r >= 0x1F680 && r <= 0x1F6FF) || // Transport and Map Symbols
 		   (r >= 0x1F700 && r <= 0x1F77F) || // Alchemical Symbols
+		   (r >= 0x2300 && r <= 0x23FF) ||   // Miscellaneous Technical (clocks, etc.)
 		   (r >= 0x2600 && r <= 0x26FF) ||   // Miscellaneous Symbols
 		   (r >= 0x2700 && r <= 0x27BF) ||   // Dingbats
-		   unicode.Is(unicode.Han, r) ||      // CJK characters
-		   r > 0x3000 {                       // Other wide characters
+		   checkAsianCharacter(r) {          // Asian characters (CJK, Korean, Japanese)
 			return true
 		}
 	}

size_emoji_test.go

@@ -69,6 +69,11 @@ func TestComplexUnicodeDetection(t *testing.T) {
 		{"中文", true, "Chinese characters"},
 		{"Hello World", false, "ASCII with space"},
 		{"测试 Test", true, "Mixed Chinese and ASCII"},
+		{"안녕하세요", true, "Korean Hangul"},
+		{"こんにちは", true, "Japanese Hiragana"},
+		{"カタカナ", true, "Japanese Katakana"},
+		{"한글 Test", true, "Mixed Korean and ASCII"},
+		{"ひらがな Test", true, "Mixed Japanese Hiragana and ASCII"},
 	}
 
 	for _, tt := range tests {
@@ -79,4 +84,30 @@ func TestComplexUnicodeDetection(t *testing.T) {
 			}
 		})
 	}
+}
+
+func TestCheckAsianCharacter(t *testing.T) {
+	tests := []struct {
+		input    rune
+		expected bool
+		name     string
+	}{
+		{'A', false, "ASCII letter"},
+		{'中', true, "Chinese character"},
+		{'한', true, "Korean Hangul"},
+		{'ㄱ', true, "Korean Jamo"},
+		{'あ', true, "Japanese Hiragana"},
+		{'カ', true, "Japanese Katakana"},
+		{'1', false, "ASCII digit"},
+		{' ', false, "Space"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := checkAsianCharacter(tt.input)
+			if got != tt.expected {
+				t.Errorf("checkAsianCharacter(%q) = %v, want %v", tt.input, got, tt.expected)
+			}
+		})
+	}
 }