integration-test: promote the qp-topic scenario into the required suite

[modelmirror]

The qp-topic scenario (token-free, credential-free — drives the shared qp-topic-measure composite over canned inputs: no-output guard, publication-gate refusal, faithful publish) is currently outside the promotion gate's required suite, deliberately: its introduction and its gate promotion are separate decisions.

Once it has a few stable live runs, promote it. The change is four synchronized edits, all pinned by existing tests (test_workflow_promote.py fails on any partial update):

1. scripts/promotion-gate.sh — add qp-topic to REQUIRED_SCENARIOS.
2. integration-test.yml — add {"scenario": "qp-topic", "engine": "claude-code"} to the all matrix.
3. promote.yml — add the scenario to the dispatch-commands help list.
4. docs/testing.md — drop the "(outside the required suite)" qualifier and adjust the required-run count in the gate paragraph (and the docs/pipeline.md scenario inventory's "outside the required suite" note from ci(qp-topic): declare the measured-file contract and pin failure reasons #1203).

Notes: the scenario spends no tokens and binds no environment variables, so adding it to the gate costs nothing per promotion; promotion-gate.sh and promote.yml are maintainer-held surfaces (the promotion gate class), so the PR waits for the maintainer even into staging.

[modelmirror]

Closed by PR #1235: qp-topic is in REQUIRED_SCENARIOS (9 required runs), the all-matrix leg is added (8 legs + the collect job), the promote.yml help list and both docs are updated — including the pre-existing collect drift (docs said seven; the true pre-change count was already 8). test_workflow_promote.py pins the sites.