artifact: add agent artifact bundle example

[ProfRandom92]

Adds a deterministic committed example artifact for the agent artifact bundle.

Includes:

• artifacts/agent_artifact_bundle_example.json
• scripts/generate_agent_artifact_bundle_example.py
• exact regeneration parity test in tests/test_agent_artifact_bundle.py

Scope

Artifact-backed reproducibility only. No timestamps, no random IDs, no network, no external APIs, and no unrelated artifact rewrites.

Validation

• python -m compileall -q scripts/agent_artifact_bundle.py scripts/generate_agent_artifact_bundle_example.py
• pytest tests/test_agent_artifact_bundle.py -q

[gemini-code-assist]

Code Review

This pull request introduces a deterministic agent artifact bundle example, including a new JSON artifact, a generation script, and comprehensive tests to verify schema stability and generator output. Feedback was provided to improve the robustness of JSON loading in the test suite by implementing error handling for missing files or malformed content and validating the resulting data structure.

[gemini-code-assist]

Adhere to the general rule for loading JSON files: handle FileNotFoundError and json.JSONDecodeError by raising a RuntimeError that includes the repo-relative path. Additionally, validate that the decoded payload is a dictionary before proceeding.

    try:
        artifact = json.loads(ARTIFACT_PATH.read_text(encoding="utf-8"))
    except (FileNotFoundError, json.JSONDecodeError) as exc:
        raise RuntimeError(f"Failed to load artifact from {ARTIFACT_PATH.as_posix()}: {exc}") from exc
    if not isinstance(artifact, dict):
        raise RuntimeError(f"Expected artifact in {ARTIFACT_PATH.as_posix()} to be a dictionary, got {type(artifact).__name__}")

References

1. When loading JSON files, handle FileNotFoundError and JSONDecodeError by raising a RuntimeError that includes a repo-relative path. Additionally, validate that the decoded payload is of the expected type (e.g., a dictionary) before proceeding.