Wave D: native AgentEvent wire + client session rewrite (SDK purged)

Server: ui-stream.ts is verbatim pi AgentEvent passthrough (SSE data
lines + [DONE]); only app-level events are the loop-level error and
turn-settled terminal; onError carries raw provider text (owner ruling).

Client: useChat + the AI-SDK transport replaced by components/session-core.ts
(SessionModel: 409 identity-retry, optimistic c_ appends, absorbed()
adoption, needsContinuation, shared consume for POST + reattach) and the
session.ts hook; the golden-master grouping canon moved client-side into
core/view.ts (projectView); scanners read the native record (phaseAt3Lh,
danglingQuestionOf, graph toolParts, plan-blocks, runner, extraction).

Coverage: the native message is the unit (fork 3) with the call+result
inseparability bond rule; view-line-less messages (markers, error
results) are invisible to coverage and never checkpointed.

Deletes: chat-transport, projection, ui-message, their tests (ported to
tests/session-core.test.ts), and the ai + @ai-sdk/react dependencies —
the Vercel SDK is fully out of the tree. Wire pins in chat-flow rewritten
onto the AgentEvent dialect (eventsOf parser).

Gates: tsc clean, 994/994 tests, eslint clean, build green; live smoke
on PORT=3004 (verbatim wire → native record).

src/core/contracts/plan.ts

@@ -115,3 +115,28 @@ export interface PlanToolResult {
 	tree: PlanTree;
 }
 
+
+// ─── the native fold (Wave D: derivePlanStatuses over LhMessage[]) ───────────
+
+import type { LhMessage } from "../native-messages.ts";
+
+/** The same derivation over the NATIVE record: quiz CALLS only (any state —
+ *  a dangling call still moves position; results feed nothing). */
+export function derivePlanStatusesLh(tree: PlanTree, messages: readonly LhMessage[]): DerivedPlanStatuses {
+	const ids = new Set(tree.nodes.map((n) => n.id));
+	const runs: string[] = [];
+	for (const m of messages) {
+		if ((m as { role?: string }).role !== "assistant") continue;
+		const content = (m as { content?: unknown }).content;
+		if (!Array.isArray(content)) continue;
+		for (const block of content as Array<{ type?: string; name?: string; arguments?: unknown }>) {
+			if (block.type !== "toolCall" || block.name !== "quiz") continue;
+			const nodeId = (block.arguments as { nodeId?: unknown } | undefined)?.nodeId;
+			if (typeof nodeId !== "string" || !ids.has(nodeId)) continue;
+			if (runs.at(-1) !== nodeId) runs.push(nodeId);
+		}
+	}
+	const current = runs.at(-1) ?? null;
+	const visited = new Set(runs.slice(0, -1));
+	return { current, visited };
+}