Export `QueueJob` type from the package root

[0xNgoo]

Summary

The QueueAdapter interface is exported, but the QueueJob type that its workers consume is not exported from the package root.

Why this matters

Exporting QueueJob lets adopters implement custom queue adapters with the correct job typing.

Task

• Export the QueueJob type from the package root entry point.
• Keep the existing QueueAdapter export working.

Acceptance criteria

• QueueJob is importable as a type from the package root.
• Existing runtime interface exports remain intact.

Testing notes

• Add or update focused tests for the behavior in this issue.
• Run bun test before opening the pull request.
• Add or update a type or export test that proves QueueJob is available from the root entry point.

Contributor notes

• Keep the change narrowly scoped to the behavior described above.
• Use Bun for commands and TypeScript for any code changes.
• Avoid adding new runtime dependencies for this issue.