Keep TAGS.md topics within GitHub's rules so one bad tag cannot block the update

[matt-edmondson]

Fixes #170

What changed

GitHubService replaces a repository's topics with a single PUT. GitHub rejects the whole set if there are more than 20 topics, or if any topic doesn't start with a letter or digit. When that happened the repository kept stale topics and the run only logged a warning. This follows the maintainer decision on the issue:

• TagsParser.Parse now trims leading and trailing - from each topic and drops any topic that ends up empty. -foo becomes foo, and --- is removed.
• After Distinct(), it keeps the first 20 topics (TagsParser.MaxTopics).
• New overloads Parse(content, IBuildLogger?) and ParseAsync(path, IBuildLogger?, ct) log a warning that names the dropped topics. PipelineService passes its logger through. The existing overloads are unchanged and simply forward with no logger, so the public API stays binary-compatible.
• A 422 on the topics PUT still doesn't fail the run.

Tests

Seven new TagsParserTests:

• 25 tags parse to 20.
• 22 tags log one warning that names tag21, tag22.
• Exactly 20 tags log no warning.
• Duplicates don't count toward the limit.
• Leading and trailing hyphens are trimmed.
• Topics made only of hyphens are dropped.
• Every returned topic matches ^[a-z0-9][a-z0-9-]{0,49}$.

To check that the tests catch the bug, I removed the trim and the cap from the fixed code. Four of the new tests then failed: the limit test, both hyphen tests, and the regex guard. The full suite passes (771 tests). The local Sonar build reports nothing new in the changed files; its one PipelineService hit, S2325 at line 421, was already there.

🤖 Generated with Claude Code

https://claude.ai/code/session_01CzB8uCZc7DWCamHvE3Qk4k

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Generated by Claude Code

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
90.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud