[API] Accept TOML text as configuration inputs

[podkidyshev]

Summary

• Accept TOML text as str for scenario/system API inputs, retaining Path inputs for configuration files.
• Adapt text inputs to the existing parser and save supplied configuration in the experiment directory.
• Require absolute test-file references when the scenario is text; file-based scenarios keep their existing relative-path behavior. Extend the existing API tests and documentation.

Test Plan

• Automated CI.
• Manual macOS standalone test: rejected a relative test reference in scenario text, accepted the equivalent absolute reference, ran Sleep, and verified completed output, saved configuration, listing, and retrieval.

PASS: TOML text, relative-path rejection, absolute test reference, saved configs and completed Sleep

Additional Notes

Based on #1060. Execution remains synchronous; background execution is added in #1062.

[coderabbitai]

Important

Draft PR not reviewed

Draft PRs are not automatically reviewed by default.

• Trigger a manual review

To automatically review draft PRs, update your CodeRabbit configuration:

reviews:
  auto_review:
    drafts: true

---

_{Comment @coderabbitai help to get the list of available commands.}