Create artifacts

Outcome: create markdown, JSON, table, code, and file outputs with stable IDs.

Module: examples.artifact_agent

python examples/artifact_agent.py

Expected result: a completed run, five artifacts, and the kinds code, file, json, markdown, and table. Muru Workspace lists metadata without inlining large content; the artifact endpoint retrieves the content by ID.

Text, bytes, and finite JSON are supported. Objects, NaN/Infinity, or invalid metadata fail before insert with a safe serialization error.

Qualified by tests/qualification/test_scenarios.py::test_artifact_scenario_creates_reopenable_supported_artifacts and the shared in-memory/SQLite artifact contracts.