Recheck dynamic dependencies before scheduling

[hermabr]

Summary

• Added interval-based dependency rechecks with recheck_interval support, including TTL caching and never semantics.
• Updated DAG tracking to distinguish declared vs runtime dependencies and refresh declared refs before scheduling.
• Improved manager scheduling so blocked/ready sets and orphan pruning stay consistent as dependencies change.
• Added tests covering dependency caching, TTL expiry, dynamic dependency refresh, and runtime dependency preservation.

Testing

• Ran/updated unit tests in tests/test_core.py for default caching, zero-interval recomputation, TTL expiry, and invalid interval handling.
• Ran/updated DAG tests in tests/test_dag.py for declared/runtime dependency tracking.
• Ran/updated worker manager tests in tests/test_worker_manager.py for dynamic recheck, pruning, root preservation, and running-node preservation.
• Not run: full test suite and integration/e2e checks.