feat: add dependency-aware ready queue for orchestration

[moltar-bot]

Summary

MosBot needs a dependency-aware ready queue so the orchestrator can tell what work is actually dispatchable.

Why

For continuous agent work, Moltar should be able to ask:

• what is ready now?
• what is blocked by dependencies?
• what is stalled?

Without this, the orchestrator has to manually reason over task lists and comments.

Minimum scope

• support task dependencies cleanly
• derive a ready view/query from existing task state + dependency state
• expose it in API and UI

Notes

This should stay generic. Avoid product/team-specific workflow states in base code.

Acceptance criteria

• Tasks can depend on other tasks
• API can return tasks that are ready to start
• A task is not considered ready if unresolved dependencies remain
• UI shows a simple ready queue / blocked-by-dependency distinction