Trim Decodex test suite inventory

[yvette-carlisle]

Summary

• collapse low-signal CLI/config/workflow parser tests into table-driven coverage
• refresh docs/reference/test-suite.md to the current 971 default-runnable tests plus one skipped live app-server test
• document remaining cleanup targets for future pruning

Verification

• cargo make check
• semantic drift audit pass for updated test-suite inventory