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/windows-hide.js

@@ -0,0 +1,41 @@
+/**
+ * @file Makes every child process on Windows start with `windowsHide: true`.
+ * The dashboard runs detached, with no console of its own, so Windows gave
+ * each console program it ran (git, npm, where, …) a NEW console window — a
+ * flash that stole focus on every poll. Node has no global default, so this
+ * patches `ChildProcess.prototype.spawn` (the one path spawn/exec/execFile/fork
+ * and their promisified forms all take) and wraps the sync exports. Require it
+ * FIRST in an entry point: a `const { execSync } = require("child_process")`
+ * evaluated before it keeps the unwrapped function. A no-op off Windows.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const DONE = Symbol.for("agenthub.windowsHide");
+
+function install(cp = require("child_process"), platform = process.platform) {
+  if (platform !== "win32" || cp[DONE]) return;
+  cp[DONE] = true;
+
+  const spawn = cp.ChildProcess.prototype.spawn;
+  cp.ChildProcess.prototype.spawn = function (options) {
+    options.windowsHide = true;
+    return spawn.call(this, options);
+  };
+
+  // spawnSync(cmd, args?, opts?), execFileSync(file, args?, opts?), execSync(cmd, opts?)
+  for (const name of ["spawnSync", "execFileSync", "execSync"]) {
+    const fn = cp[name];
+    cp[name] = function (...args) {
+      while (args.length > 1 && args[args.length - 1] == null) args.pop();
+      const last = args[args.length - 1];
+      if (args.length > 1 && typeof last === "object" && !Array.isArray(last)) {
+        args[args.length - 1] = { ...last, windowsHide: true };
+      } else {
+        args.push({ windowsHide: true });
+      }
+      return fn.apply(this, args);
+    };
+  }
+}
+
+module.exports = { install };