Skill report generator crashes when history is empty

Summary

skills/skill-creator/scripts/generate_report.py::generate_html() assumes that history contains at least one iteration. Passing an empty history raises ValueError: max() iterable argument is empty instead of producing an empty or "no iterations yet" report. This makes the report generator brittle for early live-report states, partial results, or callers that want to render a valid report before the first evaluation result exists.

Code path

• skills/skill-creator/scripts/generate_report.py:16-20 initializes history = data.get("history", []).
• skills/skill-creator/scripts/generate_report.py:25-30 handles query discovery only when history is non-empty.
• skills/skill-creator/scripts/generate_report.py:205-209 always calls max(history, ...) when choosing the best iteration, even if history is empty.
• skills/skill-creator/scripts/run_loop.py uses generate_html() for live report generation during the optimization loop, so this helper is part of the skill-creator reporting path.

Steps to reproduce

Validation level: dynamic reproduction plus source-control-flow inspection.

import importlib.util
from pathlib import Path

path = Path("skills/skill-creator/scripts/generate_report.py")
spec = importlib.util.spec_from_file_location("generate_report", path)
generate_report = importlib.util.module_from_spec(spec)
spec.loader.exec_module(generate_report)

generate_report.generate_html({"history": []})

Observed output:

ValueError: max() iterable argument is empty

Expected behavior

generate_html({"history": []}) should return a valid HTML report with summary information and an empty-state message, or at least a valid report shell that says no iterations have been recorded yet.

Actual behavior

The function raises ValueError at the best-iteration selection step:

max() iterable argument is empty

Existing coverage

I searched current issues and PRs for generate_report.py, generate_html, history, empty, ValueError, max() iterable, and Skill Description Optimization. I did not find an existing issue or PR that covers this root cause.

Suggested fix

Add an early empty-state branch before computing best_iter. For example:

• if history is empty, render the summary, legend, and a one-row/paragraph empty-state message;
• skip best-row highlighting when there is no iteration;
• keep the existing behavior unchanged for non-empty history.

Suggested tests

• Add a unit test for generate_html({"history": []}) that asserts it returns valid HTML and contains an empty-state message.
• Add a test for the existing non-empty path to ensure best-row highlighting still works.
• Add a live-report smoke test that renders before the first optimization iteration completes.

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Submitted with Codex.

Start with skills/skill-creator/scripts/generate_report.py, especially generate_html() and the best-iteration selection around lines 205-209. Reproduce the failure with generate_html({"history": []}), then add coverage for the empty-history report and the existing non-empty best-row behavior. Done means the empty input returns valid HTML with an empty-state message while non-empty reports remain unchanged.