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

client/src/components/UpdateNotifier.tsx

@@ -330,7 +330,7 @@ export function UpdateNotifier() {
           longest label is a whole sentence ("restarting the dashboard…"). */}
       <div
         ref={panelRef}
-        className="w-full max-w-2xl card shadow-2xl animate-slide-up overflow-hidden"
+        className="w-full max-w-2xl max-h-full flex flex-col card shadow-2xl animate-slide-up overflow-hidden"
       >
         {/* Header */}
         <div className="flex items-start justify-between gap-3 px-5 py-4 border-b border-border">
@@ -370,7 +370,7 @@ export function UpdateNotifier() {
         </div>
 
         {/* Body */}
-        <div className="px-5 py-4 space-y-3">
+        <div className="min-h-0 overflow-y-auto px-5 py-4 space-y-3">
           <p className="text-sm text-fg-secondary leading-relaxed">
             {pluginManaged ? t("pluginAutoNote") : release ? t("releaseLead") : t("lead")}
           </p>