feat: add AI workflow evidence demo

[ProfRandom92]

Adds a minimal deterministic local demo for the AI workflow evidence chain.

Validation:

• python -m compileall -q scripts/demo_ai_workflow_evidence.py
• pytest tests/test_demo_ai_workflow_evidence.py -q
• python scripts/demo_ai_workflow_evidence.py

[gemini-code-assist]

Code Review

This pull request introduces a script and tests for a deterministic local demo of the AI workflow evidence chain. The script processes artifact bundles and generates a PASS/FAIL summary. Review feedback focuses on adhering to repository standards for JSON processing, specifically requiring that missing or null list fields like status_short, changed_paths, and validation_evidence be treated as empty lists rather than raising errors immediately.

[gemini-code-assist]

In accordance with repository rules, treat null or missing values for expected list fields as empty lists, and raise a RuntimeError for other non-list types to maintain strictness.

    status_short = safe_pr_gate.get("status_short")
    if status_short is None:
        status_short = []
    if not isinstance(status_short, list):
        raise RuntimeError("status_short must be a list")
    changed_paths = safe_pr_gate.get("changed_paths")
    if changed_paths is None:
        changed_paths = []
    if not isinstance(changed_paths, list):
        raise RuntimeError("changed_paths must be a list")

References

1. When processing JSON data, treat null or missing values for expected list fields as empty lists, but raise a RuntimeError for other non-list types to maintain strictness.

[gemini-code-assist]

This field should default to an empty list if it is null or missing in the JSON payload, per the repository's general rules for JSON processing.

Suggested change

	validation_evidence = bundle.get("validation_evidence")
	if not isinstance(validation_evidence, list):
	raise RuntimeError("demo bundle validation_evidence must be a list")
	validation_evidence = bundle.get("validation_evidence")
	if validation_evidence is None:
	validation_evidence = []
	if not isinstance(validation_evidence, list):
	raise RuntimeError("demo bundle validation_evidence must be a list")

References

1. When processing JSON data, treat null or missing values for expected list fields as empty lists, but raise a RuntimeError for other non-list types to maintain strictness.

[gemini-code-assist]

Ensure that 'validation_evidence' is treated as an empty list if null or missing, and raise a RuntimeError for other non-list types to maintain strictness. This validation should be performed before dictionary construction.

    validation_evidence = bundle.get("validation_evidence")
    if validation_evidence is None:
        validation_evidence = []
    if not isinstance(validation_evidence, list):
        raise RuntimeError("validation_evidence must be a list")

References

1. When processing JSON data, treat null or missing values for expected list fields as empty lists, but raise a RuntimeError for other non-list types to maintain strictness.