test: register new covering tests in Stryker collector

[diegosouzapw]

Summary

Register six recently added unit test files in the explicit Stryker TAP collector. They contribute eight missing coverage relationships across accountFallback, auth, comboStructure, and quotaScoring. The runtime, mutated modules, thresholds, and frozen baselines are unchanged.

Validation

• Exact base 2c9938d14e92ca927469a5e9daf81c532097928c: strict collection gate RED with eight missing relationships across four modules.
• Same strict gate after the six additions: PASS.
• Six added files plus collector contract suite: 34 PASS, zero failed/skipped. Existing database cleanup warning output remains in the receipt; no errors were suppressed.
• Prettier, diff check, and branch pre-commit checks passed.

The full nightly mutation run was not executed; this fixes test discovery, not proof of a mutation score. Draft recovery slice; combined release/main acceptance remains pending.