artifacts: the height ratchet fixed, invert switch persisted + restyled (release polish 7.2)

- bridge measures the BODY (scrollHeight + rect + margins) instead of the
  viewport-clamped documentElement — documentElement.scrollHeight latches
  at the parent's own height, so demos could grow but never shrink on
  window resize (owner-reported); smoke: 1036 → 2386 → 1036 px
- invert now PERSISTS as details.ui.inverted on the steer record, written
  by the silent artifact-ui route (dismissal pattern: no wake, no SSE) and
  seeded through the projection (SubagentArtifactData.ui); survives
  navigation + reload, never enters teacher context or exports
- invert restyled as the house Toggle switch (settings controls) on both
  cards; demo header is the caption grammar: 'INTERACTIVE DEMO — title'
  left (title normal-case, same size/tracking), switch + download far
  right; figure header: label left, switch/download/open far right

1439 tests green (route + pure-seam pins added); live smoke passed

src/core/contracts/jobs.ts

@@ -271,12 +271,36 @@ export interface SubagentResultMeta {
 export interface SubagentArtifactData {
 	kind: JobKind;
 	result: ResearchResult | DemoResult | VisualResult | PdfResult;
+	/** The learner's pinned UI state (invert switch) riding the record. */
+	ui?: { inverted?: boolean };
 }
 
 /** A result steer's marker details: the UI's meta + artifact in one
  *  payload (the projection splits it into metadata + data part). */
 export interface SteerDetails extends SubagentResultMeta {
 	result: ResearchResult | DemoResult | VisualResult | PdfResult;
+	/** LEARNER UI state pinned onto the artifact (owner, 2026-10-07): the
+	 *  invert switch's position, persisted so navigating away and back (or
+	 *  restarting) keeps it. A VIEW preference — never enters the teacher's
+	 *  context, never exports (the markdown engine reads `result` only). */
+	ui?: { inverted?: boolean };
+}
+
+/** Set a steer message's ui.inverted (pure): returns a NEW message array
+ *  with the target's details updated — no-op (same array) when the message
+ *  is missing or not an invertible artifact steer. The silent route's
+ *  whole body. */
+export function setSteerUiInverted(
+	messages: readonly LhMessage[],
+	messageId: string,
+	inverted: boolean,
+): LhMessage[] {
+	return messages.map((m) => {
+		if (m.id !== messageId) return m;
+		const d = (m as LhMarkerMessage).details as Partial<SteerDetails> | undefined;
+		if (!d || (d.kind !== "demo" && d.kind !== "visual")) return m;
+		return { ...m, details: { ...d, ui: { ...d.ui, inverted } } } as LhMessage;
+	});
 }
 
 /** Anything the wake pipeline may queue and deliver — a native marker. */

src/core/view.ts

@@ -368,6 +368,7 @@ function projectMarker(marker: LhMarkerMessage, out: LhViewMessage[]): void {
 			const artifact = marker.details as {
 				kind: SubagentArtifactData["kind"];
 				result: SubagentArtifactData["result"];
+				ui?: SubagentArtifactData["ui"];
 			};
 			out.push({
 				id: marker.id,
@@ -375,7 +376,11 @@ function projectMarker(marker: LhMarkerMessage, out: LhViewMessage[]): void {
 				metadata: { subagentResult: meta },
 				parts: [
 					textPart(marker.content),
-					{ type: "data-subagent-artifact", id: `sa_${marker.id}`, data: { kind: artifact.kind, result: artifact.result } },
+					{
+						type: "data-subagent-artifact",
+						id: `sa_${marker.id}`,
+						data: { kind: artifact.kind, result: artifact.result, ui: artifact.ui },
+					},
 				],
 			});
 			return;