Make existing controls real + add robustness pass

Wire up controls that were rendered but inert, expose unused server
actions, and harden the live update path.

Controls now functional:
- File priority dropdowns (Content tab) now persist via new
  setFilePriority server action
- Context menu: Set location, Limit download/upload rate, Set share
  limit (wire setSavePath/setDownLimit/setUpLimit/setRatioLimit)
- Trackers sidebar filter actually filters (snapshot now carries
  per-torrent trackerHosts)

Robustness:
- Grid updates cells in place when row order/columns are unchanged
  (preserves text selection/scroll, no per-second listener re-bind)
- Boot retries until the server responds; SSE drops show a
  "Reconnecting" banner; failed actions/add/delete surface a toast
- Prune selection/detail for torrents that disappear
- Drop Backspace-as-delete (kept Delete)

Cleanup:
- Remove pseudo DHT/PeX/LSD names from the real-tracker host pool in
  mock data (they leaked into announce URLs and the sidebar)
- Remove dead detailTab import/export

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

public/js/detail.js

@@ -9,8 +9,6 @@ let currentHash = null;
 let refreshTimer = null;
 let detailHeight = 300; // px, persisted across re-renders so resizing sticks
 
-export function detailTab() { return activeTab; }
-
 export function renderDetailShell(hash, host) {
   currentHash = hash;
   // Drive the container's grid track (persists across row clicks / re-renders),
@@ -58,7 +56,7 @@ async function loadTab() {
       if (activeTab === 'general') body.innerHTML = renderGeneral(await api.torrent(currentHash));
       else if (activeTab === 'trackers') body.innerHTML = renderTrackers(await api.trackers(currentHash));
       else if (activeTab === 'peers') body.innerHTML = renderPeers(await api.peers(currentHash));
-      else if (activeTab === 'content') body.innerHTML = renderFiles(await api.files(currentHash));
+      else if (activeTab === 'content') { body.innerHTML = renderFiles(await api.files(currentHash)); bindFilePriorities(body); }
       else if (activeTab === 'pieces') body.innerHTML = renderPieces(await api.pieces(currentHash));
     } catch { /* ignore transient */ }
   };
@@ -176,6 +174,13 @@ function renderFiles(files) {
   </tbody></table>`;
 }
 
+function bindFilePriorities(body) {
+  const hash = currentHash;
+  body.querySelectorAll('.prio-sel').forEach((sel) =>
+    sel.addEventListener('change', () =>
+      api.action('setFilePriority', [hash], { index: +sel.dataset.file, priority: +sel.value })));
+}
+
 /* ---------- Pieces ---------- */
 function renderPieces(data) {
   const { pieces, pieceSize, pieceCount } = data;