Returns metadata only (run_id, suite, timestamps, counts) — not the full
list of test cases. Use `qa_get_run` for that.

Filters are applied in this order: suite (exact match), since, until.
Results are sorted by `started_at` ascending. Pagination via limit/offset.

Returns:
    Markdown table or JSON depending on response_format. JSON shape:
    {
        "total": int,
        "count": int,
        "offset": int,
        "has_more": bool,
        "next_offset": int | null,
        "items": [
            {"run_id": str, "suite": str, "started_at": iso8601,
             "summary": {"total","passed","failed","skipped","errors"}}
        ]
    }

Error response: string starting with "Error:".

By default, only failed/error tests are listed in the body (to keep context
small). Set `include_passed=true` for the full inventory.

Returns:
    Markdown or JSON depending on response_format. JSON returns the full
    RunReport model conforming to schemas/run-report.v1.json.

Error response: string starting with "Error: ..." (e.g., "Error: Run not found").

`run_a` is treated as baseline (older), `run_b` as newer.

Categories returned:
    regressions          passed in A, failed/error in B (highest priority)
    fixes                failed/error in A, passed in B
    persistent_failures  failed in both
        same_error       fingerprints match → same root cause
        different_error  fingerprints differ → root cause changed
    new_tests            in B but not A
    removed_tests        in A but not B
    other_changes        transitions involving skipped (low priority)

Flakiness detection requires N>2 runs and is not in this tool. Use the
weekly_regression_review prompt to orchestrate multi-run analysis.

Returns:
    Markdown summary or JSON of the full ComparisonResult model.

Error response: string starting with "Error: ...".