fix: preserve Java normalization semantics for line terminators

csharp/PhoneNumbers.Test/TestPhoneNumberUtil.cs

@@ -471,6 +471,30 @@ public void TestNormaliseReplaceAlphaCharacters()
                 PhoneNumberUtil.Normalize(inputNumber));
         }
 
+        [Fact]
+        public void TestNormaliseStripAlphaCharactersWithLineTerminators()
+        {
+            // Java's VALID_ALPHA_PHONE_PATTERN uses dot without DOTALL and matches the whole input.
+            foreach (var separator in new[] { "\n", "\r", "\r\n", "\u0085", "\u2028", "\u2029" })
+            {
+                foreach (var input in new[]
+                {
+                    separator + "1800FLOWERS",
+                    "1800F" + separator + "LOWERS",
+                    "1800FLOWERS" + separator,
+                })
+                {
+                    Assert.Equal("1800", PhoneNumberUtil.Normalize(input));
+                }
+            }
+
+            // Other whitespace is accepted by Java's dot and must not disable vanity conversion.
+            foreach (var separator in new[] { " ", "\t", "\v", "\f" })
+            {
+                Assert.Equal("18003569377", PhoneNumberUtil.Normalize("1800F" + separator + "LOWERS"));
+            }
+        }
+
         [Fact]
         public void TestNormaliseOtherDigits()
         {

csharp/PhoneNumbers/PhoneNumberUtil.cs

@@ -209,7 +209,15 @@ private static bool IsValidAlphaPhone(StringBuilder number)
             {
                 var lower = number[i] | 0x20;
                 if ((uint)(lower - 'a') <= 'z' - 'a' && ++alpha == 3)
+                {
+                    // Java's normalization pattern matches the whole input without DOTALL.
+                    for (var j = 0; j < number.Length; j++)
+                    {
+                        if (number[j] is '\n' or '\r' or '\u0085' or '\u2028' or '\u2029')
+                            return false;
+                    }
                     return true;
+                }
             }
             return false;
         }

csharp/PhoneNumbers/PhoneNumberUtil.net.cs

@@ -663,7 +663,8 @@ private static bool IsValidAlphaPhone(string number)
                 var lower = number[i] | 0x20;
                 if ((uint)(lower - 'a') <= 'z' - 'a' && ++alpha == 3)
                 {
-                    return true;
+                    // Java's normalization pattern matches the whole input without DOTALL.
+                    return number.AsSpan().IndexOfAny("\n\r\u0085\u2028\u2029") < 0;
                 }
             }