fix: v2.5.3 — Windows workspace folders, picker on top, no console flashes

A workspace could not be created on Windows: "cwd must be an absolute path"
for D:\…, because createLane/canonicalCwd tested for a leading "/".

- lanes.js: path.isAbsolute/path.resolve; canonicalCwd stops at any root (a
  missing drive looped forever); resolveLaneByCwd and /ensure accept "\" too
- native-dialog.js: the Windows picker gets an invisible TopMost owner form,
  shown first — an ownerless dialog from the background server opened behind
  the browser, or hidden
- windows-hide.js: every child process on Windows starts with windowsHide,
  required first by the server and the detached scripts (a console window
  flashed per git/npm call)
- Confirm/update/clear-data modals and the quota panel scroll instead of
  overflowing a short window

server/lib/native-dialog.js

@@ -95,7 +95,12 @@ function dialogCommands(kind, dir, platform = process.platform) {
           "-NoProfile",
           "-STA",
           "-Command",
-          `[Console]::OutputEncoding = [Text.Encoding]::UTF8; Add-Type -AssemblyName System.Windows.Forms; ${dialog}; if ($d.ShowDialog() -eq 'OK') { [Console]::Out.Write(${result}) } else { exit 1 }`,
+          // 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 }`,
         ],
       ],
     ];