Group Project Run Artifacts

[drown0315]

Parent

#98

What to build

Add Project Run artifact grouping without changing existing single-Scenario run
artifacts. A Project Run should create one batch-level run directory under
.runs/, place each Scenario Run in its own child directory, and write a
machine-readable project_run_report.json at the batch root. Existing Scenario
Run reports and timelines should remain usable inside child directories.

Acceptance criteria

• Project Run creates one batch-level run directory under .runs/.
• Each Scenario Run in the batch writes to a child run directory.
• Child run directories keep the existing Scenario Run layout.
• The batch root contains project_run_report.json.
• project_run_report.json records discovery root, Scenario file paths, execution order, per-Scenario status, report paths, Project Run status, duration, command inputs, and environment-level failure details when present.
• The first version does not generate a batch-level HTML report.
• Existing report and diff behavior for Scenario Run directories is preserved.
• Tests cover directory creation, relative report paths, child Scenario Run layout, all-passed reports, partially failed reports, and environment-level failure reports.

Blocked by

• Discover Project Scenarios #99