fix: revoke stale egress access

[steipete]

Summary

• bind mediated-egress tickets and accepted sockets to the server-derived lease principal
• reauthorize and register sockets atomically with lease-share changes
• revoke both halves of live or restored sessions when manage access is removed or downgraded
• fail closed restored legacy egress attachments that have no recoverable principal

Closes #730

Verification

• npm run format:check --prefix worker
• npm run lint --prefix worker
• npm run check --prefix worker
• npm test --prefix worker (700 tests)
• npm run build --prefix worker
• source-blind behavior validation: 6 passed, 0 failed, 0 blocked
• autoreview: clean, no actionable findings
• git diff --check

Security and compatibility

• Egress still requires owner or manage access; use-only access remains insufficient.
• Admission and share updates use the same coordinator lock, closing the consume-to-register race.
• Existing principal-less restored egress sockets are closed once with policy code 1008 and must reconnect with a fresh ticket.
• No credential, configuration, or protocol-message changes.