Close out Phase 6 L7 proof gaps

[kacy]

Summary

• add restart-focused proof for VIP steering reapplication and loop rejection through the socket path
• turn Phase 6 from an open remaining-work list into explicit first-cut exit criteria
• make the one-request-per-connection boundary an intentional first-cut choice rather than an implicit limitation

Commit

• 8fae64c Close out Phase 6 L7 proof gaps

Testing

• targeted zig build test runs were executed one at a time for the new listener-restart steering test, the new loop-rejection-after-restart socket test, and the broader rollout-status compile path
• each targeted run hit the explicit timeout without emitted failures