Fix error detection for current Git output

[sergiou87]

Summary

Update three error classifications while preserving legacy diagnostics:

• Accept lowercase and legacy uppercase branch rename failures.
• Recognize current and legacy revert-conflict advice, including git revert --no-commit.
• Recognize staged, unstaged, and combined changes blocking rebase or pull with rebase.

Revert-specific diagnostics take priority over generic merge-conflict output. Detection still requires conflict advice rather than treating every failed revert as a conflict.

Add 30 regression tests covering nine real bundled Git scenarios, legacy output, CRLF line endings, negative cases, and classification ordering. Document the supported behavior.

Validation

• Confirmed 14 new tests failed before changing the patterns.
• All 115 tests pass after the fix.
• Library, declarations, and examples build successfully.
• Formatting and diff checks pass.
• Runtime validation used bundled macOS Git 2.53.0.
• Windows runtime validation remains for CI; matching producers were verified in Git for Windows v2.53.0.windows.4.