refactor: collapse isFlagBoundaryChar into a single switch

Author: claude

internal/docgen/mintlify.go

@@ -189,16 +189,13 @@ func backtickFlags(s string) string {
 	return strings.Join(parts, "```")
 }
 
+// isFlagBoundaryChar reports whether c is a valid character before a flag —
+// anything that is not a word char (\w), backtick, slash, or dash.
 func isFlagBoundaryChar(c byte) bool {
-	// A flag must be preceded by start-of-string or a character that is not
-	// a word char, slash, dash, or backtick.
-	if c == '/' || c == '-' || c == '`' {
+	switch {
+	case c == '/', c == '-', c == '`', c == '_':
 		return false
-	}
-	if c == '_' {
-		return false
-	}
-	if (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') {
+	case c >= 'a' && c <= 'z', c >= 'A' && c <= 'Z', c >= '0' && c <= '9':
 		return false
 	}
 	return true