fix: scope outbox publishing to active repository

[jose-matos-9281]

Summary

• centralize outbox repository resolution so scoped publish uses the same repository for fetch, success marking, and failure marking
• run the full publish cycle inside a fresh write scope when scoped runtime is configured without an active scope
• add regression tests for scoped routing, worker isolation, fallback behavior, and verify the full pytest suite passes

Verification

• uv run pytest