test: add comprehensive live end-to-end coverage

[jmagar]

Summary

• add registry-driven coverage for every public HTTP, Phoenix Channel, MCP, dashboard, extension, command, lifecycle, persistence, security, capacity, and compatibility surface
• exercise shared scenarios through real Bandit/Phoenix transport and pinned Chromium/Manifest V3 adapters
• add deterministic replay, executable fault injection, attested/redacted artifacts, strict run ownership, and zero-residue cleanup
• harden credential revocation, browser erasure, challenge instance binding, audit lifecycle, and broker fault isolation discovered during consolidated review

Verification

• mix precommit: 147/147
• protocol PR: 72/72
• Chromium smoke: 4/4
• official MCP compatibility: 5/5
• extension tests: 60/60
• stress tests: 12/12; real seeded stress run 9/9
• CI/contracts: 38/38
• coverage inventory: 177/179 mapped plus 2 approved exclusions, 100%
• final live cleanup: zero failures and owned run root absent

Review history

Implementation was completed before review. One consolidated Lavra review and one Phoenix-focused review were run; all actionable findings were remediated and verified before publication.