fix(plex): a Restart does not replay on a reload or a Forward onto the player

fromStart rode in history.state._sub, so reloading the player entry restarted
the item from 0 again and the progress checkpoint overwrote its resume point.
A sub-view config can now say what the history entry keeps of a view.

frontend/src/components/plexSubUrl.test.ts

@@ -76,3 +76,18 @@ describe("PLEX_SUB_URL decode guards", () => {
     expect(U.decode("")).toBeNull();
   });
 });
+
+describe("PLEX_SUB_URL entry", () => {
+  // E28 review E1: the Restart click must not replay on a reload / Forward onto the player entry.
+  it("keeps the player without its one-shot fromStart, and every other view whole", () => {
+    const entry = U.entry!;
+    expect(entry({ kind: "player", id: "7", queue: ["7", "8"], fromStart: true })).toEqual({
+      kind: "player",
+      id: "7",
+      queue: ["7", "8"],
+      fromStart: undefined,
+    });
+    const info = { kind: "info", id: "7" } as const;
+    expect(entry(info)).toBe(info);
+  });
+});