[sds]

Adds 17 examples covering the remaining untested validation, plugin loading and signing, branch configuration, processor contention, and platform fallback paths. Local line coverage reaches 100% (3,822/3,822), with all existing tests preserved and coverage filters unchanged.

The signing tests exposed an absolute-path bug: joining an absolute command path to the repository root produced a nonexistent path, so command contents were omitted from approval signatures. Resolve command paths with File.expand_path and verify that changes to both absolute and relative command files require fresh approval.

Validation:

• Fresh full suite: 2,090/2,090 examples verified, zero failures.
• Fresh LCOV report: 3,822/3,822 executable lines covered (100%).
• All pre-commit checks pass, including RuboCop.
• All 20 GitHub Actions jobs pass across Ruby 3.3, 3.4, and 4.0 on Linux and Windows.
• All 18 CI coverage artifacts combined: 3,824/3,824 executable lines covered (100%). Each Linux Ruby version independently reports 100% as well.