fix: ProcessPoolTaskRunner now checks upstream task states in wait_for dependencies

[devin-ai-integration]

Summary

Fixes a bug where ProcessPoolTaskRunner silently ignored upstream task failures in wait_for dependencies. Downstream tasks would execute even when their upstream dependencies had failed, instead of being set to NotReady as ThreadPoolTaskRunner correctly does.

Closes #21117

Root cause

_resolve_futures_and_submit called wait() on wait_for futures but then passed wait_for=None to the subprocess, so the subprocess task engine's _wait_for_dependencies was never invoked to check upstream states.

Fix

After waiting for futures to complete, extract their terminal State objects and pass them as wait_for to the subprocess. State objects are picklable (unlike futures) and the existing task engine machinery (_wait_for_dependencies → resolve_to_final_result) already handles State objects — raising UpstreamTaskError for non-completed upstreams, which results in the NotReady state.

Important review notes

• State picklability: The fix relies on State (Pydantic model) surviving cloudpickle serialization to the subprocess. This should be fine but is worth verifying.
• allow_failure annotations: If wait_for items are wrapped in allow_failure(), the annotation is not preserved through the state extraction. However, this edge case was already broken before this PR (the existing wait(list(wait_for)) call would fail on allow_failure-wrapped items). Fixing that is out of scope.

Checklist

• This pull request references any related issue by including "closes <link to issue>"
• If this pull request adds new functionality, it includes unit tests that cover the changes
• If this pull request removes docs files, it includes redirect settings in mint.json.
• If this pull request adds functions or classes, it includes helpful docstrings.

Links

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[codspeed-hq]

Merging this PR will not alter performance

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_{Comparing devin/OSS-7764-1773438866 (a30c032) with main (bba455a)}

[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 2 additional findings.