Add nil-element validation for chunks in ExecutionResult and Payload

[zhangchiqing]

Add nil-element validation for the [Chunks] slice in [ExecutionResult] and nested chunk validation in [Payload]. Rejects CBOR-decoded null elements in chunk lists before they become trusted model objects.

This PR depends on #8688. It is part of a PR stack that splits up #8668.

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Summary by CodeRabbit

• Bug Fixes

  • Invalid execution data containing nil chunks is now rejected with a clear validation error.
  • Payload creation also reports the location of nil chunks within execution results.

• Tests

  • Added coverage to verify nil chunks are consistently rejected when creating execution results and payloads.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Advanced

Run ID: d6ab1155-2dfc-4c7c-b8f6-e461945207dc

📥 Commits

Reviewing files that changed from the base of the PR and between 28cb04c and e46fddf.

📒 Files selected for processing (4)

• model/flow/execution_result.go
• model/flow/execution_result_test.go
• model/flow/payload.go
• model/flow/payload_test.go

Included review availability: Your plan provides up to 4 included reviews per hour; 2 remain after this review.

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📝 Walkthrough

Walkthrough

The execution result and payload constructors now reject nil chunk elements. Tests cover both validation paths and their indexed error messages.

Changes

Nil chunk validation

Layer / File(s)	Summary
Constructor validation and tests model/flow/execution_result.go, model/flow/payload.go, model/flow/execution_result_test.go, model/flow/payload_test.go	NewExecutionResult and NewPayload reject nil chunk elements with indexed errors. Tests verify nil results and the reported error messages.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~5 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to 3dfe3

This change only rejects malformed inputs that contain empty chunk entries when building execution results and block payloads, returning a clear error instead of accepting them. Valid data behaves exactly as before and both rejection paths are covered by tests, so there is no notable merge risk.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: adding nil-element validation for chunks in both ExecutionResult and Payload.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 4 functions across 4 files.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch leo/nil-validation-execution-result-payload

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[github-actions]

Dependency Review

✅ No vulnerabilities or license issues or OpenSSF Scorecard issues found.

Scanned Files

None

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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