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.

server/lib/native-dialog.js

@@ -61,6 +61,25 @@ function startDir(start) {
   return os.homedir();
 }
 
+// user32 calls PowerShell has no cmdlet for: `Front` makes a window the
+// foreground one from a background process (see dialogCommands).
+const WIN_FRONT = [
+  '[DllImport("user32.dll")] public static extern bool ShowWindow(IntPtr h, int n);',
+  '[DllImport("user32.dll")] public static extern bool SetForegroundWindow(IntPtr h);',
+  '[DllImport("user32.dll")] public static extern bool BringWindowToTop(IntPtr h);',
+  '[DllImport("user32.dll")] public static extern IntPtr GetForegroundWindow();',
+  '[DllImport("user32.dll")] public static extern uint GetWindowThreadProcessId(IntPtr h, IntPtr p);',
+  '[DllImport("user32.dll")] public static extern bool AttachThreadInput(uint a, uint b, bool on);',
+  '[DllImport("kernel32.dll")] public static extern uint GetCurrentThreadId();',
+  "public static void Front(IntPtr h) {",
+  "  uint fg = GetWindowThreadProcessId(GetForegroundWindow(), IntPtr.Zero);",
+  "  uint me = GetCurrentThreadId();",
+  "  bool joined = fg != 0 && fg != me && AttachThreadInput(me, fg, true);",
+  "  BringWindowToTop(h); SetForegroundWindow(h);",
+  "  if (joined) AttachThreadInput(me, fg, false);",
+  "}",
+].join("\n");
+
 /** The candidate dialog commands for a platform, in order of preference. */
 function dialogCommands(kind, dir, platform = process.platform) {
   const title = TITLES[kind];
@@ -88,19 +107,36 @@ function dialogCommands(kind, dir, platform = process.platform) {
         ? "$d = New-Object System.Windows.Forms.FolderBrowserDialog; $d.SelectedPath = $env:AGENTHUB_PICK_START; $d.Description = $env:AGENTHUB_PICK_TITLE"
         : "$d = New-Object System.Windows.Forms.OpenFileDialog; $d.InitialDirectory = $env:AGENTHUB_PICK_START; $d.Title = $env:AGENTHUB_PICK_TITLE";
     const result = kind === "dir" ? "$d.SelectedPath" : "$d.FileName";
+    // The server is a background process, and Windows keeps one from bringing
+    // a window forward: an ownerless dialog opened at the BOTTOM of the
+    // z-order, behind the browser. So the dialog gets a TopMost owner, made
+    // the foreground window by joining the current foreground thread's input
+    // (AttachThreadInput — the lock exempts it). The first ShowWindow of a
+    // process started with windowsHide is turned into a hide; a throwaway call
+    // spends it, or the owner stays hidden and takes the dialog down with it.
+    const script = [
+      "$ProgressPreference = 'SilentlyContinue'",
+      "[Console]::OutputEncoding = [Text.Encoding]::UTF8",
+      "Add-Type -AssemblyName System.Windows.Forms",
+      `Add-Type -Namespace AgentHub -Name Win -MemberDefinition '${WIN_FRONT}'`,
+      "$o = New-Object System.Windows.Forms.Form",
+      "$o.TopMost = $true; $o.ShowInTaskbar = $false; $o.FormBorderStyle = 'None'; $o.Opacity = 0; $o.Width = 1; $o.Height = 1; $o.StartPosition = 'CenterScreen'",
+      "[void][AgentHub.Win]::ShowWindow($o.Handle, 1)",
+      "$o.Show()",
+      "[AgentHub.Win]::Front($o.Handle)",
+      dialog,
+      `if ($d.ShowDialog($o) -eq 'OK') { [Console]::Out.Write(${result}) } else { exit 1 }`,
+    ].join("\n");
+    // -EncodedCommand: the C# above carries double quotes, which Windows
+    // PowerShell's own command-line parsing mangles inside -Command.
     return [
       [
         "powershell.exe",
         [
           "-NoProfile",
           "-STA",
-          "-Command",
-          // The server is a background process, and Windows will not let one
-          // bring a window to the front: an ownerless dialog opened BEHIND the
-          // browser (or hidden — the first ShowWindow of a process started
-          // with windowsHide). An invisible TopMost owner, shown first, takes
-          // that first ShowWindow and keeps the dialog on top.
-          `[Console]::OutputEncoding = [Text.Encoding]::UTF8; Add-Type -AssemblyName System.Windows.Forms; $o = New-Object System.Windows.Forms.Form; $o.TopMost = $true; $o.ShowInTaskbar = $false; $o.FormBorderStyle = 'None'; $o.Opacity = 0; $o.Width = 1; $o.Height = 1; $o.Show(); $o.Activate(); ${dialog}; if ($d.ShowDialog($o) -eq 'OK') { [Console]::Out.Write(${result}) } else { exit 1 }`,
+          "-EncodedCommand",
+          Buffer.from(script, "utf16le").toString("base64"),
         ],
       ],
     ];