feat: add panel and multi-model CodSpeed benchmarks

[AzulGarza]

Summary

• Add a large_panel_df fixture (100 series × 500 points) for benchmarks where preprocessing cost is visible
• Parametrize test_timeseries_dataset_from_df with small and large sizes
• Add test_foundation_forecast_multi_model (3 and 5 DatasetTouchingModel instances) to measure multi-model dataset construction overhead
• Extend the CodSpeed core workflow to run the new orchestration benchmarks

These benchmarks establish baselines on main before #18 (shared panel processing) merges. After #18 lands, CodSpeed on that PR should show speedups on test_foundation_forecast_multi_model and test_timeseries_dataset_from_df[large].

Phase 2 (panel micro-benchmarks: process_panel_from_df, from_panel, etc.) will be added in PR #18 once those APIs exist.

Test plan

• CodSpeed core job passes (benchmarks-core)
• Confirm new benchmarks appear in CodSpeed report:
  • test_timeseries_dataset_from_df[large]
  • test_foundation_forecast_multi_model[3-models]
  • test_foundation_forecast_multi_model[5-models]
• Rebase PR feat: reuse shared panel processing across forecasters (refresh of #2) #18 onto this branch after merge and verify CodSpeed delta

Made with Cursor

[codspeed-hq]

Merging this PR will not alter performance

✅ 7 untouched benchmarks
🆕 4 new benchmarks

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
🆕	Simulation	test_timeseries_dataset_from_df[large]	N/A	180.1 ms	N/A
🆕	Simulation	test_timeseries_dataset_from_df[small]	N/A	10.8 ms	N/A
🆕	Simulation	test_foundation_forecast_multi_model[3-models]	N/A	578 ms	N/A
🆕	Simulation	test_foundation_forecast_multi_model[5-models]	N/A	965 ms	N/A

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_{Comparing feat/panel-codspeed-benchmarks (8f5472b) with main (8e5e745)}

[Copilot]

🟢 Approval recommended

No unresolved issues were identified.

Pull request overview

Adds CodSpeed benchmarks for large-panel preprocessing and multi-model orchestration.

Changes:

• Adds a 100-series × 500-point fixture.
• Parametrizes dataset benchmarks by panel size.
• Adds 3-model and 5-model orchestration benchmarks.
• Runs the new benchmarks in CodSpeed core.

File summaries

File	Description
tests/benchmarks/test_orchestration.py	Adds multi-model dataset construction benchmarks.
tests/benchmarks/test_core.py	Benchmarks small and large datasets.
tests/benchmarks/conftest.py	Defines the large panel fixture.
.github/workflows/codspeed.yml	Includes orchestration benchmarks in CodSpeed core.

Review details

• Files reviewed: 4/4 changed files
• Comments generated: 0
• Review effort level: Lite

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