feat: v2.5.4 — Query Explorer folded into Sessions, Windows picker and paths

- Sessions page tabs: Sessions · Events · Agents. QueryExplorer.tsx became
  AgentsTable.tsx (agents only — sessions and events already had tabs);
  /query redirects to /sessions?view=agents and leaves the sidebar.
  GET /api/query is unchanged and still answers all three entities.
- Windows picker opens in front: -EncodedCommand script spends the hidden
  first ShowWindow that windowsHide gives the process, then brings the TopMost
  owner forward via AttachThreadInput (v2.5.3's owner was itself hidden).
- Session page Resume/Fork/Open pane: owningLane and sessionWorktreeName
  match Windows folders (either separator), with a test.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "agenthub",
-  "version": "2.5.3",
+  "version": "2.5.4",
   "bin": {
     "agenthub": "bin/agenthub.js"
   },