feat(changelog): remember the newest change the reader has seen

First-run setup marks a new reader up to date, since changes mean nothing
before you've used the app. An absent marker therefore means an install
from before the changelog, which is what lets the launch be announced to
existing readers once.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

src/client/App.tsx

@@ -19,7 +19,7 @@ import { useProgress } from "./state/useProgress.ts";
 import { useDailyLog, type DailyLogMap } from "./state/useDailyLog.ts";
 import { useTasks } from "./state/useTasks.ts";
 import { useAmounts } from "./state/useAmounts.ts";
-import { adoptNewLanes, usePrefs, type Prefs } from "./state/usePrefs.ts";
+import { adoptNewLanes, firstRunPrefs, usePrefs, type Prefs } from "./state/usePrefs.ts";
 import { buildExportData, parseImportData, triggerDownload } from "./state/export.ts";
 import { snapDayWidth } from "./state/zoom.ts";
 import { useCustom, type EventDraft } from "./state/useCustom.ts";
@@ -487,11 +487,7 @@ export function App() {
           <Welcome
             available={ordered}
             onConfirm={(chosen, chosenView) =>
-              update({
-                onboarded: true,
-                hiddenGames: games.filter((g) => !chosen.includes(g)),
-                view: chosenView,
-              })
+              update(firstRunPrefs(games, chosen, chosenView))
             }
           />
         </Shell>

src/client/state/usePrefs.ts

@@ -7,6 +7,7 @@ import { KEYS, readJson, writeJson } from "./storage.ts";
 import type { TimelineGroup } from "./lanes.ts";
 import { DEFAULT_THEME_CHOICE, type ThemeChoice } from "./theme.ts";
 import { DEFAULT_DAY_WIDTH, snapDayWidth } from "./zoom.ts";
+import { ENTRIES, newestId } from "../../shared/changelog.ts";
 
 /**
  * Which of the two views the reader is looking at.
@@ -192,6 +193,30 @@ export interface Prefs {
   routineGames?: LaneId[] | undefined;
   /** Games already asked "track its weekly tasks?", so the question is asked once. */
   routinesAsked?: LaneId[] | undefined;
+  /**
+   * The newest changelog entry the reader dismissed (PRD F18). Absent means
+   * unrecorded, not "seen nothing": first-run setup sets it, so an absent value
+   * is an install from before the changelog, shown the launch window once.
+   */
+  changelogSeen?: string | undefined;
+}
+
+/**
+ * What finishing first-run setup writes. A new reader is marked up to date
+ * with the changelog: a list of changes means nothing before you've used the
+ * thing it changes.
+ */
+export function firstRunPrefs(
+  games: readonly LaneId[],
+  chosen: readonly LaneId[],
+  view: View,
+): Partial<Prefs> {
+  return {
+    onboarded: true,
+    hiddenGames: games.filter((g) => !chosen.includes(g)),
+    view,
+    changelogSeen: newestId(ENTRIES),
+  };
 }
 
 export function defaults(): Prefs {
@@ -321,6 +346,10 @@ export function restorePrefsValue(incoming: unknown): Prefs {
     }
   }
 
+  if (result.changelogSeen !== undefined && typeof result.changelogSeen !== "string") {
+    result.changelogSeen = undefined;
+  }
+
   // Built-in tasks: string arrays, or absent.
   for (const key of ["routineGames", "routinesAsked"] as const) {
     const value: unknown = result[key];

test/changelog.test.ts

@@ -63,3 +63,22 @@ describe("what a reader has not seen", () => {
     expect(compareUrl("https://r", "a1b2c3d", "e4f5a6b")).toBe("https://r/compare/a1b2c3d...e4f5a6b");
   });
 });
+
+describe("the seen marker in prefs", () => {
+  test("restore keeps a string and drops anything else", async () => {
+    const { restorePrefsValue } = await import("../src/client/state/usePrefs.ts");
+    expect(restorePrefsValue({ changelogSeen: "check-in-goals" }).changelogSeen).toBe("check-in-goals");
+    expect(restorePrefsValue({ changelogSeen: 7 }).changelogSeen).toBeUndefined();
+    expect(restorePrefsValue({}).changelogSeen).toBeUndefined();
+  });
+
+  test("first-run setup marks everything seen", async () => {
+    const { firstRunPrefs } = await import("../src/client/state/usePrefs.ts");
+    expect(firstRunPrefs(["genshin", "hsr"], ["hsr"], "soon")).toEqual({
+      onboarded: true,
+      hiddenGames: ["genshin"],
+      view: "soon",
+      changelogSeen: newestId(ENTRIES),
+    });
+  });
+});