Improve GitHub reporting and tool execution

[emmett2020]

Summary

• add GitHub API reporting/comment handling coverage and update reporting flow
• add LLVM 22 tool installation support for Ubuntu CI/regression runs
• improve CMake dependency resolution for libgit2 across package layouts
• fix hunk row boundary handling for inline comments

Verification

• cmake -S . -B build-review -GNinja
• cmake --build build-review
• ./build-review/tests/test
• cmake --build build
• ./build/tests/test
• git diff --check