[Skylm808]

Which issue or RFC does this PR close?

Closes #2071.

Rationale for this change

The scheduler activation test compares every completion log's trace ID with the first root span's trace ID. Each activation creates an independent root trace, so multiple valid activations can cause the test to fail.

What changes are included in this PR?

• Wait for at least two activations to consistently exercise the multiple-activation scenario.
• Close the runtime before inspecting logs and finished spans.
• Match completion logs to root spans by trace ID and span ID, including occurrence counts.
• Verify that activations have distinct trace IDs, root spans have no parent, and completion logs do not retain the startup request ID.

Are there any user-facing changes?

No. This change only updates a test; runtime behavior and public APIs are unchanged.

How was this change tested?

Validated locally with Python 3.11.16:

• Confirmed that waiting for two activations causes the original assertion to fail for both memory and experience.

• Ran test_scheduler.py: 18 passed.

• Ran the following related tests with four workers: 50 passed.

  .venv/bin/python -m pytest -n 4 \
    tests/builtin/runtime/test_scheduler.py \
    tests/builtin/runtime/test_processing_scheduler.py \
    tests/builtin/runtime/test_artifact_processing.py -q

[hidb4ai]

LGTM