Recover blocked searches, fall through to the next peer, rebuild the UI

Measured against a live instance: 47 failed jobs against 33 imported. Three
independent causes, all of which ended the request.

The Soulseek server filters some artist names. "Michael Jackson Billie Jean"
and bare "Michael Jackson" both return zero responses; "Billie Jean" returns
1083 files. The Weeknd, Kanye West and Frank Ocean behave the same way. Since
pick_and_enqueue sent exactly one query of `artist title`, every request for a
filtered artist failed reporting "searched 0 files" -- 28 of 29 occurrences.
search_queries() now walks a ladder, loosest last, ending at the bare title,
and escalates only when a search underdelivers so the common case still costs
one search. Dropping the artist from the query does not mean ignoring it:
match_ratio() looks for it in the folder path, where an organised share puts it.

A rejected transfer ended the request. pick_and_enqueue kept a running maximum
and discarded every runner-up, so "Transfer rejected: File not shared." -- a
per-file condition where candidate two almost always works -- was terminal, as
were timeouts and slskd's 500 on an unreachable peer. The ranked list is now
persisted on the job row, ordered to put a different peer next, and
try_next_candidate() advances through it. A job fails only once the list is
exhausted, and then reports every peer it tried and what each one said.

norm() destroyed every non-ASCII character, so "Beyonce" never matched
Beyonce, nor Bjork Bjork, nor Dont Don't. It now folds accents and drops
apostrophes while leaving & as a separator.

Also: availability outranks format in score(), because a FLAC behind 5000
queued users used to beat an immediately available MP3; transfers that stall or
that slskd forgets are abandoned instead of sitting in `downloading` forever;
searches are deleted only once finished, since deleting one mid-flight makes
slskd throw an optimistic-concurrency error and lose the record; a failed
search POST is retried rather than failing the job on one blip.

The UI moves to a sidebar shell -- rail at tablet, bottom bar on phones -- with
neutral chrome and the sampled artwork colour confined to hero areas rather
than repainting the whole interface. Adds URL routing, a primitive set under
components/ui, and a request sheet showing the attempt ladder. Fixes
hover:bg-glass-hi, which was never a valid class, so track rows and the search
field had no hover or focus state at all; a reduced-motion path that could
strand elements at opacity 0; the login page's hardcoded palette; and the
missing 404 and error boundaries.

tests/test_acquisition.py covers this path against a faked slskd. It had none.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

web/lib/nav.ts

@@ -0,0 +1,95 @@
+"use client";
+
+import * as React from "react";
+
+/**
+ * URL state for a statically exported app.
+ *
+ * There was none: `tab` and the album/artist view lived in React state alone,
+ * so a refresh always dumped you back at the welcome screen, the browser Back
+ * button did nothing, and no view could be linked to anyone. `output: "export"`
+ * rules out dynamic route segments, so the state rides in the query string and
+ * is driven through the History API.
+ */
+export type Tab =
+  | "search"
+  | "discover"
+  | "jobs"
+  | "review"
+  | "bulk"
+  | "settings"
+  | "admin";
+
+export type Nav = {
+  tab: Tab;
+  view?: "album" | "artist";
+  id?: string;
+  q?: string;
+};
+
+const TABS: Tab[] = ["search", "discover", "jobs", "review", "bulk", "settings", "admin"];
+
+export function parse(search: string): Nav {
+  const p = new URLSearchParams(search);
+  const raw = p.get("tab");
+  const tab = (TABS as string[]).includes(raw || "") ? (raw as Tab) : "search";
+  const v = p.get("view");
+  return {
+    tab,
+    view: v === "album" || v === "artist" ? v : undefined,
+    id: p.get("id") || undefined,
+    q: p.get("q") || undefined,
+  };
+}
+
+export function href(n: Nav): string {
+  const p = new URLSearchParams();
+  if (n.tab !== "search") p.set("tab", n.tab);
+  if (n.view) p.set("view", n.view);
+  if (n.id) p.set("id", n.id);
+  if (n.q) p.set("q", n.q);
+  const s = p.toString();
+  return s ? `?${s}` : "/";
+}
+
+/**
+ * Reads the URL and writes it back, without Next's router.
+ *
+ * `next/navigation`'s useSearchParams forces a Suspense boundary under static
+ * export and re-renders the tree on every keystroke of a search query. The
+ * History API is enough for what this needs and keeps Back working.
+ *
+ * useSyncExternalStore rather than useState-in-an-effect: the URL is external
+ * state that React does not own, and this is the hook designed for that. It
+ * also gets the static-export case right — the prerendered HTML has no URL to
+ * read, so the server snapshot is the empty query, and the client subscribes
+ * from its first render without a mismatch.
+ */
+const LOCATION_EVENT = "muse:navigate";
+
+function subscribe(cb: () => void) {
+  window.addEventListener("popstate", cb);
+  window.addEventListener(LOCATION_EVENT, cb);
+  return () => {
+    window.removeEventListener("popstate", cb);
+    window.removeEventListener(LOCATION_EVENT, cb);
+  };
+}
+
+const clientSearch = () => window.location.search;
+const serverSearch = () => "";
+
+export function useNav(): [Nav, (n: Nav, replace?: boolean) => void] {
+  const search = React.useSyncExternalStore(subscribe, clientSearch, serverSearch);
+  const nav = React.useMemo(() => parse(search), [search]);
+
+  const go = React.useCallback((n: Nav, replace = false) => {
+    const url = href(n);
+    if (replace) window.history.replaceState(null, "", url);
+    else window.history.pushState(null, "", url);
+    // pushState does not fire popstate, so tell our own subscribers.
+    window.dispatchEvent(new Event(LOCATION_EVENT));
+  }, []);
+
+  return [nav, go];
+}