fix: preserve campaign timestamp ordering

[VrtxOmega]

Summary

• capture the campaign start timestamp when supervisor state is initialized
• carry that timestamp through finalization so serialized campaign intervals cannot end before they start
• add a regression assertion for chronological ordering

Reproduction

The documented sealed dry-run path produced this transcript interval on current main:

started_at: 2026-07-29T04:02:41.402147+00:00
ended_at:   2026-07-29T04:02:41.402125+00:00

ended_at was evaluated before Pydantic generated the default started_at, so the interval was inverted even though both fields were structurally valid.

After this change, a fresh run produced:

started_at: 2026-07-29T04:05:44.835058+00:00
ended_at:   2026-07-29T04:05:44.860988+00:00
order valid: true

Validation

• pytest -q tests/test_supervisor.py tests/test_runtime_truth.py — 13 passed
• uv sync --extra dev --extra research-gepa && make ci-pr — Ruff and mypy passed; 648 unit tests passed, 1 skipped; 25 offline golden tests passed
• README sealed dry-run campaign completed successfully and the serialized transcript satisfied started_at <= ended_at

[chatgpt-codex-connector]

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