Avoid false duplicate detection for repeated `--batch` options without values

[Seddryck]

Problem

System.CommandLine tokenizes --batch=a into an option identifier and an argument, so repeated equals syntax is counted correctly.

However, this command:

run "trim" --batch --batch

can treat the second --batch token as the first option's value. A raw token count therefore counts both occurrences and incorrectly reports a duplicate option.

Expected behavior

Duplicate detection should use the parsed option result rather than raw tokens.

Use:

result.GetResult(batch)?.IdentifierTokenCount ?? 0

so only actual option identifiers are counted.

Acceptance criteria

• --batch=a --batch=b is still detected as a duplicate when duplicates are not allowed.
• --batch --batch does not produce a false duplicate solely because the second token was parsed as the first option's value.
• Add regression tests covering both equals syntax and repeated bare option tokens.

[Seddryck]

Reviewed as part of 2.0