feat: API pipeline run list has execution summary

[yuechao-qin]

TL;DR

Added execution summary to pipeline run responses to provide aggregated information about pipeline execution status (GET /api/pipeline_runs/)..

What changed?

• Added execution_summary field to PipelineRunResponse dataclass
• Renamed _get_execution_status_stats to _get_execution_stats_and_summary to return both stats and summary

How to test?

1. Create a pipeline run with multiple nodes in different states
2. Call the list API with include_execution_stats=True
3. Verify the response contains both execution stats and execution summary
4. Check that the summary correctly reports total nodes, ended nodes, and completion status

Run the new test cases in tests/test_api_server_sql.py:

pytest tests/test_api_server_sql.py

Why make this change?

This closes #87

[yuechao-qin]

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Learn more

• feat: GetExecutionNodes API returns number of total and ended nodes #99
• test: Add tests for GetGraphExecution API #98
• feat: API pipeline run get has execution summary #97
• feat: API pipeline run list has execution summary #96 👈 (View in Graphite)
• refactor: Function to get execution status stats #95
• feat: Model to track node states and has_ended flag #94
• master

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