feat(client): read decks/cards/study from IndexedDB first

Switch deckAtom, cardsByDeckAtomFamily, noteTypesAtom, and studyDataAtom
to a stale-while-revalidate pattern: read from IndexedDB synchronously,
trigger sync in the background, and refetch on sync_complete. When local
is empty, await a single bootstrap pull before deciding there's no data.

Add study-builder to assemble StudyCards from LocalCard + Note + NoteType
+ field values, replacing the server /study endpoint dependency. The
study session can now run end-to-end offline.

Disable submit on all write modals when offline since writes still
require the server. Add a "Showing cached data" hint to the sync status
indicator. Drop cacheStudyCards (cards arrive via regular sync pull now)
and update page tests to reflect that lists no longer refresh by hitting
the GET API.

1 files changed, 27 insertions, 33 deletions

diff --git a/src/client/atoms/study.ts b/src/client/atoms/study.ts
index 17519de..115bbcd 100644
--- a/src/client/atoms/study.ts
+++ b/src/client/atoms/study.ts
@@ -1,19 +1,12 @@
 import { atomFamily } from "jotai-family";
 import { atomWithSuspenseQuery } from "jotai-tanstack-query";
 import { getStartOfStudyDayBoundary } from "../../shared/date";
-import { apiClient } from "../api/client";
-import type { CardStateType } from "../db";
-import { cacheStudyCards, type ServerStudyCard } from "../sync";
+import { localDeckRepository } from "../db/repositories";
+import { buildStudyCards, type StudyCardView } from "../db/study-builder";
 import { createSeededRandom, shuffle } from "../utils/random";
+import { ensureBootstrap } from "./sync";
 
-export interface StudyCard extends ServerStudyCard {
-	state: CardStateType;
-	noteType: {
-		frontTemplate: string;
-		backTemplate: string;
-	};
-	fieldValuesMap: Record<string, string>;
-}
+export type StudyCard = StudyCardView;
 
 export interface StudyDeck {
 	id: string;
@@ -25,35 +18,36 @@ export interface StudyData {
 	cards: StudyCard[];
 }
 
+async function loadStudyData(deckId: string): Promise<StudyData | null> {
+	const deck = await localDeckRepository.findById(deckId);
+	if (!deck || deck.deletedAt !== null) return null;
+	const cards = await buildStudyCards(deckId);
+	const seed = getStartOfStudyDayBoundary().getTime();
+	return {
+		deck: { id: deck.id, name: deck.name },
+		cards: shuffle(cards, createSeededRandom(seed)),
+	};
+}
+
 // =====================
-// Study Session - Suspense-compatible
+// Study Session - Suspense-compatible, IndexedDB-first
 // =====================
 
 export const studyDataAtomFamily = atomFamily((deckId: string) =>
 	atomWithSuspenseQuery(() => ({
 		queryKey: ["decks", deckId, "study"],
 		queryFn: async (): Promise<StudyData> => {
-			// Fetch deck and due cards in parallel
-			const [deckRes, cardsRes] = await Promise.all([
-				apiClient.rpc.api.decks[":id"].$get({ param: { id: deckId } }),
-				apiClient.rpc.api.decks[":deckId"].study.$get({ param: { deckId } }),
-			]);
-
-			const deckData = await apiClient.handleResponse<{ deck: StudyDeck }>(
-				deckRes,
-			);
-			const cardsData = await apiClient.handleResponse<{
-				cards: StudyCard[];
-			}>(cardsRes);
-
-			// Cache cards in IndexedDB so reviews can be submitted offline.
-			await cacheStudyCards(cardsData.cards);
-
-			const seed = getStartOfStudyDayBoundary().getTime();
-			return {
-				deck: deckData.deck,
-				cards: shuffle(cardsData.cards, createSeededRandom(seed)),
-			};
+			let data = await loadStudyData(deckId);
+			if (data) {
+				ensureBootstrap();
+				return data;
+			}
+			await ensureBootstrap();
+			data = await loadStudyData(deckId);
+			if (!data) {
+				throw new Error(`Deck not found: ${deckId}`);
+			}
+			return data;
 		},
 	})),
 );