slskd: /soulseek search + downloads on the Workspace/Panel framework

Two panels (search + transfers) via WorkspaceView, coordinating over the
soulseek:refresh channel. Adds the page-title rule and documents the
route conventions in CLAUDE.md.

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

src/apps/officer-web/App.tsx

@@ -41,6 +41,7 @@ export function App() {
             <Route path="/plans" element={<Dashboard.Plans />} />
             <Route path="/files" element={<Dashboard.FilesScreen />} />
             <Route path="/music" element={<Dashboard.MusicScreen />} />
+            <Route path="/soulseek" element={<Dashboard.SoulseekScreen />} />
             <Route path="/system-monitor" element={<Dashboard.SystemMonitorScreen />} />
             <Route path="/activity" element={<Dashboard.ActivityScreen />} />