fix(executor): attribute parallel-batch exceptions to the correct action (#415)

[Yuthika10]

Summary

In the parallel-batch path of Executor.execute, when an action raised an exception, the failure was always recorded against batch[0] - the first action in the batch - regardless of which action actually raised. asyncio.gather returns results positionally, so the exception's position in batch_results corresponds to batch[position], but that position was discarded and batch[0] was hardcoded. Since _analyze_dependencies groups independent actions into multi-action batches, a non-first action raising would name the wrong action in the resulting ActionResult and the audit trail.

This fixes the attribution to use the position, and extracts the batch-result collection into a small testable method so the behavior can be unit-tested.

Closes #415

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Type of change

• Bug fix
• New feature / enhancement
• Documentation update
• Tests / CI
• Performance improvement
• Refactor (no functional change)

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Changes made

• daemon/pilot/agents/executor.py: extracted the parallel-batch result handling into _collect_batch_results(batch, batch_results, results), which iterates with enumerate and attributes a raised exception to batch[position] instead of batch[0]. The success branch is unchanged (it already used the idx returned by execute_single_action).
• daemon/tests/test_executor_batch_attribution.py: new unit tests - a non-first action raising is attributed to the correct action, the first-action case still works (guards against simply flipping the bug), and an all-success batch reports no failure.

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How to test

1. pytest daemon/tests/test_executor_batch_attribution.py -v - the three tests pass.
2. The key test, test_exception_attributed_to_failing_action_not_first, fails against the old batch[0] code and passes with the fix - it builds a 3-action batch where the second action raises and asserts the failure names that action.
3. ruff check and ruff format --check on the two files are clean.

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Checklist

• I have read the CONTRIBUTING.md
• My code follows the existing code style
• I have added/updated tests where applicable
• All existing tests pass (pytest for backend, npm run test for frontend)
• I have updated documentation if needed
• I have tested on at least one platform (Windows / macOS / Linux)

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Screenshots / recordings (if UI change)

N/A — no UI change.

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GSSoC declaration

• This contribution is made under the GSSoC 2026 program
• I have not plagiarised code from other repositories

[Yuthika10]

Hi @VyomKulshrestha just sent a PR for issue #415 - has passed all 6 checks. Can you please review the code? Would love your feedback on this for any further improvements.

[Yuthika10]

Hi @VyomKulshrestha! Can you plese go thorugh this PR?