fix(playwright): drill into antd input inside row-select-checkbox span

The data-test="row-select-checkbox" attribute lives on the wrapper <span>
that TableCollection's rowSelection.renderCell puts around antd's checkbox
originNode. Playwright's .check() requires an <input type="checkbox"> and
throws "Not a checkbox or radio button" on the span. Drill into the real
input so bulk-select interactions work across chart/dashboard/dataset lists.

Also lift toHaveCount(0) post-delete assertions to TIMEOUT.API_RESPONSE
(15s) so slow server-side propagation doesn't flake the row-removed check.

Verified locally: 3 consecutive runs of chart-list + dashboard-list +
dataset-list against docker-light all exit 0; 7 previously-failing
bulk-select tests pass first try in every run.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>