feat(evaluation): add single-arm baseline comparisons

[frf12]

Which issue or RFC does this PR close?

Follow-up to #1247. No standalone issue.

Rationale for this change

The evaluation console previously required every SWE-bench Pro task to execute both OFF and ON, even when an existing historical result was the intended comparison point. That doubled execution cost and latency and provided no durable way to reuse trusted results across batches.

What changes are included in this PR?

• Add off_on, on_only, and off_only execution modes across runner, worker, artifacts, reports, API contracts, and persisted batch requests.
• Preserve the existing paired OFF/ON comparison when both Arms run, while omitting unavailable Arm data from single-Arm reports.
• Add immutable single-Arm baseline snapshots with task outcomes, token metrics, exact attempt provenance, dataset/harness revisions, model settings, and PowerContext revision.
• Add APIs for saving baselines, listing newest-first baseline records, checking compatibility, selecting multiple baselines, and computing historical comparisons without rerunning evaluation.
• Add report-page controls for saving ON or OFF baselines, selecting historical comparisons, and viewing a richer baseline library.
• Migrate the evaluation runtime schema from 2 to 3 and retain backward compatibility for existing paired report artifacts.
• Accept standard JSON arrays in strict baseline-selection requests, covering the deployed 422 regression.
• Update the evaluation README and focused backend/frontend tests.

Are there any user-facing changes?

Yes. A batch may now run OFF + ON, ON only, or OFF only. Completed aggregate reports can save any executed Arm as one of multiple immutable baselines. Later reports can compare an executed Arm with multiple compatible historical baselines without rerunning tasks. The baseline library is ordered by save time descending.

Existing paired evaluation and report behavior remains available. The SQLite runtime schema migrates automatically; this does not change the public PowerContext HTTP API outside the evaluation console.

How was this change tested?

• uv run pytest -q tests --disable-warnings — 1033 passed
• uv run ruff check src tests
• uv run ty check src
• npm test -- --run — 15 files, 96 tests passed
• npm run build
• git diff --check
• Deployed to the m0 evaluation environment and smoke-tested schema consistency, all three treatment modes, baseline candidates, selection PUT, historical comparison, existing paired reports, and frontend assets.

AI usage statement

Implemented and tested with OpenAI Codex (GPT-5) under human-directed product review.

[github-actions]

license-eye has checked 805 files.

Valid	Invalid	Ignored	Fixed
608	3	194	0

Click to see the invalid file list

• evaluation/src/powercontext_eval/web/baselines.py
• evaluation/web/src/components/BaselineLibrary.tsx
• evaluation/web/src/components/BatchLauncher.test.tsx

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```bash

docker run -it --rm -v $(pwd):/github/workspace apache/skywalking-eyes header fix

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	/*
	/*
	* Copyright (c) 2026 OceanBase.
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	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
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	/*
	/*
	* Copyright (c) 2026 OceanBase.
	*
	* Licensed under the Apache License, Version 2.0 (the "License");
	* you may not use this file except in compliance with the License.
	* You may obtain a copy of the License at
	*
	* http://www.apache.org/licenses/LICENSE-2.0
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	* distributed under the License is distributed on an "AS IS" BASIS,
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	/*