practice: the agent's data drawer — full transparency on every conclude card (round 17)

Owner ask (2026-10-06): reveal everything the agent filled in when
writing the problem and concluding it, at the very bottom of the
conclude card, collapsible, arriving collapsed.

The fields, both calls:
- problem: mode (recall/discrimination/composition), target
  proposition ids, statement, modelSolution (the last two ARE the
  visible card — the drawer shows the metadata only)
- conclude: outcome, hint rung (R0–R5/null), miss class
  (cue/discrimination/execution/careless/structural/null), retest.

Seams: problemInputForConclude (native-messages) walks the reveal's
walk and folds the WHOLE problem-call input onto the conclude part
(projectView join; same refused-pose law — an unacked pose folds
nothing); ArtifactPartProps grows problemInput. Targets resolve to
proposition NAMES at render (one lazy module-cached /api/graph fetch;
failure degrades to raw ids — observability never breaks the card).
The drawer: divider + chevron 'AGENT'S DATA' toggle (mono-caps
eyebrow register), definition rows with mono values, 'untagged'/
'none' honest empties, absent entirely when the calls filled nothing
(the dismissal line, legacy bare records).

src/core/contracts/chat.ts

@@ -298,6 +298,10 @@ export interface ArtifactPartProps {
 		toolCallId: string;
 		input?: unknown;
 		output?: unknown;
+		/** The pose-side fold (owner round 17): the whole problem-call
+		 * arguments joined onto the conclude part by projectView — the
+		 * observability drawer's data. */
+		problemInput?: unknown;
 		/** The view-seam join for conclude cards (owner round, 2026-10-05):
 		 *  the modelSolution committed at POSE time, folded onto the part by
 		 *  projectView — the reveal is never re-authored. */