Fix LangSet.hasLang() to compare against FcLangEqual instead of FcTrue

FcLangSetHasLang returns FcLangResult enum values:
- FcLangEqual (0): Exact match
- FcLangDifferentTerritory (1): Same language, different territory
- FcLangDifferentLang (2): Different language

The previous comparison to FcTrue (1) caused:
- Exact matches (0) to incorrectly return false
- Partial matches (1) to incorrectly return true

This fix changes the comparison to FcLangEqual (0) so hasLang()
correctly returns true only for exact language matches.

Fixes emoji font detection which relies on checking for 'und-zsye'
language tag support.

pkg/fontconfig/lang_set.zig

@@ -11,8 +11,12 @@ pub const LangSet = opaque {
         c.FcLangSetDestroy(self.cval());
     }
 
+    pub fn addLang(self: *LangSet, lang: [:0]const u8) bool {
+        return c.FcLangSetAdd(self.cval(), lang.ptr) == c.FcTrue;
+    }
+
     pub fn hasLang(self: *const LangSet, lang: [:0]const u8) bool {
-        return c.FcLangSetHasLang(self.cvalConst(), lang.ptr) == c.FcTrue;
+        return c.FcLangSetHasLang(self.cvalConst(), lang.ptr) == c.FcLangEqual;
     }
 
     pub inline fn cval(self: *LangSet) *c.struct__FcLangSet {
@@ -32,3 +36,26 @@ test "create" {
 
     try testing.expect(!fs.hasLang("und-zsye"));
 }
+
+test "hasLang exact match" {
+    const testing = std.testing;
+
+    // Test exact match: langset with "en-US" should return true for "en-US"
+    var fs = LangSet.create();
+    defer fs.destroy();
+    try testing.expect(fs.addLang("en-US"));
+    try testing.expect(fs.hasLang("en-US"));
+
+    // Test exact match: langset with "und-zsye" should return true for "und-zsye"
+    var fs_emoji = LangSet.create();
+    defer fs_emoji.destroy();
+    try testing.expect(fs_emoji.addLang("und-zsye"));
+    try testing.expect(fs_emoji.hasLang("und-zsye"));
+
+    // Test mismatch: langset with "en-US" should return false for "fr"
+    try testing.expect(!fs.hasLang("fr"));
+
+    // Test partial match: langset with "en-US" should return false for "en-GB"
+    // (different territory, but we only want exact matches)
+    try testing.expect(!fs.hasLang("en-GB"));
+}