HasMinimumLines/HasMaximumLines/HasExactLines don't count a lone \r or Unicode line separator, contradicting IsMultiLine/IsSingleLine: "a\rb" is multi-line but has "1 line" #299

What's wrong

The five line-related validation attributes in Semantics.Strings/Validation/Attributes/Format/ disagree on what a line break is.

• IsSingleLineAttribute and IsMultiLineAttribute treat '\n', '\r' and any UnicodeCategory.LineSeparator character as a line break.
• HasMinimumLinesAttribute, HasMaximumLinesAttribute and HasExactLinesAttribute count lines as value.Count(c => c == '\n') + 1.

The \r\n "don't double count" block in those three changes nothing. It computes crlfCount + (lfTotal - crlfCount) + 1, which equals the original lfTotal + 1.

Failure scenario

For "a\rb", and for "a b":

Why it matters

• These attributes are meant to be combined. [HasMaximumLines(1)] lets through strings that [IsSingleLine] rejects.
• [IsMultiLine, HasMinimumLines(2)] rejects a string that IsMultiLine just accepted.
• Classic Mac line endings, and text containing U+2028, bypass line-count limits entirely.

Suggested fix

Add one shared helper, for example internal static int CountLines(string value), and use it in all three Has*Lines attributes. It should treat \r\n as one break, and a lone \r, \n, U+2028 or U+2029 as one break each. Remove the no-op CRLF block.

Acceptance criteria

• "a\rb", "a\nb", "a\r\nb" and "a b" each count as 2 lines in HasMinimumLines, HasMaximumLines and HasExactLines.
• "a\r\n\r\nb" counts as 3.
• Tests cover each line ending.