Resolve output references used as dictionary keys

[CAOShurong]

Summary

• resolve OutputReference objects used as dictionary keys as well as values
• preserve nested key references through Monty serialization, including inside MSONable objects
• reject unhashable resolved keys and duplicate resolved keys instead of silently losing data
• add unit and run_locally regression coverage for BUG: Dictionaries with output references as keys do not resolve #838

Fixes #838.

Additional dependencies introduced (if any)

None.

TODO (if any)

None.

Checklist

• Code follows the repository style (pre-commit passes).
• Private helper docstrings and type annotations are included.
• Tests cover the new behavior and failure boundaries.
• Focused tests, the full suite, package builds, and a clean-wheel workflow were run.

Verification

• pytest tests/core/test_reference.py tests/managers/test_local.py::test_output_reference_as_dictionary_key -q: 18 passed
• pytest -q: 140 passed, 8 skipped, 1 xfailed on a successful full run. A repeat encountered three Windows same-timestamp assertions in unrelated local-manager tests; two of the representative failures reproduced on the exact base commit.
• pre-commit run --files src/jobflow/core/reference.py tests/core/test_reference.py tests/managers/test_local.py: passed
• python -m build: sdist and wheel built successfully
• clean install of the built wheel: the issue reproduction returned {'text': 'c', 'test': 'text'}

Disclosure: this pull request was prepared with assistance from OpenAI Codex; the implementation and verification evidence are provided here for maintainer review.

[utf]

Hi @CAOShurong, thank you for this. Are you able to resolve the conflicts with the existing branch? Note, we have just merged #870 which may overlap here.