fix(nav): the address follows the view through overlays, reloads and Back (review round 1)

- A URL mirror names the view again on every entry Back or Forward lands on, so a change made
  under a dialog, a drawer or a sub-view is not undone by the next reload.
- A view pushed from the entry a reload under a dialog started from no longer inherits its overlay
  mark; a reload under two overlays closes onto the page in one step.
- The linked player reopens over a live search, gives itself up when its list moves first, and
  plays alone over an emptied playlist; a capped Files list keeps the link it cannot resolve.
- The Feed press over a channel ends the search; leaving a search ends its asked mark; Files and
  Playlists searches end with their page; the feed always names its view and debounces its search.
- Search-box keys are declared per module and kept out of the client log below TRACE.
- Writers outside lib/ go through codecs; the URL contract scans computed keys, overlay writers and
  two-line reads, and holds every page to a bookmark round trip (Config, Activity, Playlists and the
  Files sort and viewer added).

frontend/src/features/navigation/NavigationProvider.ytSearch.dom.test.tsx

@@ -188,6 +188,57 @@ describe("NavigationProvider · the YouTube search in the address", () => {
     expect(search().get("ytn")).toBeNull();
   });
 
+  it("a search left by Back and reached again by Forward is not asked for", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    expect(result.current.ytSearchAsked).toBe(true);
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&q=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    window.history.replaceState({ sfPage: "feed", _yt: "lofi" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearch).toBe("lofi");
+    expect(result.current.ytSearchAsked).toBe(false);
+  });
+
+  it("a search left in place is not asked for when it is opened again by a link", () => {
+    window.history.replaceState(null, "", "/?page=feed&yt=lofi");
+    const { result } = render();
+    act(() => result.current.askYtSearch());
+    stubNoEntryBelow();
+    act(() => result.current.exitYtSearch());
+    window.history.replaceState({ sfPage: "feed" }, "", "/?page=feed&yt=lofi");
+    act(() => {
+      window.dispatchEvent(new PopStateEvent("popstate", { state: window.history.state }));
+    });
+    expect(result.current.ytSearchAsked).toBe(false);
+  });
+
+  it("the Feed press over a channel opened from the search opens the plain feed", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.openChannel("UC1"));
+    act(() => result.current.setPage("feed"));
+    expect(result.current.channelView).toBeNull();
+    expect(result.current.ytSearch).toBeNull();
+    expect(search().get("yt")).toBeNull();
+  });
+
+  it("a channel closed in place over the search names the search again", () => {
+    const { result } = render();
+    act(() => result.current.enterYtSearch("lofi"));
+    act(() => result.current.setYtCount(40));
+    act(() => result.current.openChannel("UC1"));
+    expect(search().get("yt")).toBeNull();
+    stubNoEntryBelow();
+    act(() => result.current.closeChannel());
+    expect(result.current.ytSearch).toBe("lofi");
+    expect([search().get("yt"), search().get("ytn")]).toEqual(["lofi", "40"]);
+  });
+
   it("a page switch takes the search off the address", () => {
     const { result } = render();
     act(() => result.current.enterYtSearch("lofi"));