FEAT GUI: Configure a scenario from selected dataset examples

Start with the Datasets table, frontend\src\components\Scenarios\ScenarioDetail.tsx, its extracted form/estimate/launch boundaries, shared parameter controls, and scenariosApi; also review item 12-14 prerequisites and coordinate with #2653. Trace how selected IDs and existing scenario progress/history are handled before defining the flow. Done means mocked component/routing tests cover exact selections, validation, preview/estimate/confirmation, cancellation state, and duplicate-launch prevention without privileged datasets.

Is your feature request related to a problem? Please describe.

Selecting several dataset examples should lead to a configurable scenario, not concatenate unrelated prompts into chat or immediately call a target. Users need to see the exact selection and execution configuration before launching.

Work item 15 of 17 in #2744. Technical prerequisites: the table/selection IDs plus items 12-14. Keep not ready yet until promoted.

Describe the solution you'd like

Add explicit multi-select to the explorer and a Configure scenario action. Preserve selected IDs across pages, make selected-versus-visible counts clear, and allow reviewing/removing/clearing the selection. Do not turn a page selection into an implicit select-all-matching query.

For one example the existing chat import actions remain available. For multiple examples, use the scenario path rather than concatenation or a queue of chat drafts.

Open a Scanner configuration flow using existing reusable form/estimate/launch pieces. Prefill exactly the selected examples, prompt sending, no additional converters, and a compatible configured scorer default. Allow target and scorer selection and collect missing required objectives explicitly. Show setup guidance when no compatible scorer or target is configured.

Preview the selected population and effective configuration before explicit launch confirmation. On launch, reuse the normal scenario queue/progress/history. Preserve explorer state when cancelling or returning. No new persistent named dataset or generated scenario source file is created by opening the form.

Acceptance criteria:

• Selections survive pagination and can be reviewed/cleared without selecting hidden unrequested examples.
• Configure scenario performs no target call and uses exact IDs, not a reconstructed dataset filter.
• Default settings mean prompt sending only, no extra converters, and an explicit compatible scorer.
• Missing objectives, invalid/stale selections, incompatible presets, and empty configuration have clear validation.
• Preview, estimate, confirmation, and launch agree on the selected examples; duplicate launch is prevented.
• Cancel/Back/navigation preserve the user's browse state, and success goes to existing scenario progress/history.
• Component/routing tests cover the flow using mocked APIs and no privileged datasets.

Describe alternatives you've considered, if relevant

Do not build another launch page with duplicated state, add batch chat behavior, or launch directly from a selection checkbox. Advanced technique/converter controls are item 16; this item should deliver the useful default flow first.

Additional context

Start with the Datasets table, frontend\src\components\Scenarios\ScenarioDetail.tsx and its extracted form/estimate/launch boundaries, shared parameter controls, and scenariosApi. Coordinate with #2653 instead of growing a second monolithic configuration component. Follow frontend style/test instructions.