Coming back to the feed shows it as it was left

Leaving the feed keeps it in Services/FeedMemory.cs (posts, waiting posts, cursors and scroll; ten minutes, for the same
feed of the same persona), so coming back from a thread or a profile shows it again at once, older pages included,
instead of reading it anew; newer posts come behind the "new" button and through the stream as before.
tests/e2e FeedMemoryTests goes to a thread and back without a new read of the home timeline; the whole suite passes
(123, 5 skipped).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

tests/e2e/Actions/FeedMemoryTests.cs

@@ -0,0 +1,47 @@
+using decePubClient.E2E.Support;
+
+using Microsoft.Playwright;
+
+namespace decePubClient.E2E.Actions
+{
+	// Coming back to the feed from a thread shows it as it was left, with its older pages, without reading it again
+	// (Services/FeedMemory.cs).
+	public sealed class FeedMemoryTests(Browser browser)
+	{
+		[Fact]
+		public async Task The_feed_comes_back_from_a_thread_as_it_was_left()
+		{
+			var persona = Pasture.Personas().First();
+			await using var session = await SignIn.As(browser, persona);
+			var page = session.Page;
+			await Results.Cell("client.action.feed-memory", "privapub", persona.UserName, async () =>
+			{
+				await page.GotoAsync($"{Pasture.Site}/");
+				await page.EvaluateAsync("() => localStorage.removeItem('FeedFilter')");
+				await page.GotoAsync($"{Pasture.Site}/");
+				var feed = page.Locator("[data-feed-count]");
+				await page.Locator("article[data-uri]").First.WaitForAsync(new() { Timeout = 30000 });
+				// an older page too when there is one, so there is more to keep than the first
+				await page.EvalOnSelectorAsync("#feed-scroll", "root => root.scrollTop = root.scrollHeight");
+				await Pasture.Eventually(async () => int.Parse(await feed.GetAttributeAsync("data-feed-count") ?? "0") > 20, 10);
+				var count = int.Parse(await feed.GetAttributeAsync("data-feed-count") ?? "0");
+
+				var homeReads = 0;
+				page.Request += (_, request) =>
+				{
+					if (request.Url.Contains("/api/v1/timelines/home") && !request.Url.Contains("min_id"))
+						homeReads++;
+				};
+				await page.EvalOnSelectorAsync("#feed-scroll", "root => root.scrollTop = 0");
+				await page.Locator("article[data-uri] footer a[href^='expand/']").First.ClickAsync();
+				await page.WaitForURLAsync("**/expand/**");
+				await page.GoBackAsync();
+				await page.Locator("article[data-uri]").First.WaitForAsync(new() { Timeout = 10000 });
+
+				Assert.True(int.Parse(await feed.GetAttributeAsync("data-feed-count") ?? "0") >= count, "the feed came back shorter than it was left");
+				Assert.Equal(0, homeReads);
+				await session.AssertGuards();
+			}, page);
+		}
+	}
+}