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/__tests__/windows-hide.test.js

@@ -0,0 +1,50 @@
+/**
+ * @file Tests for server/lib/windows-hide.js: on win32 every child process,
+ * async or sync, is started with `windowsHide: true`; elsewhere nothing changes.
+ * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
+ */
+
+const { test } = require("node:test");
+const assert = require("node:assert/strict");
+const { install } = require("../lib/windows-hide");
+
+function fakeCp() {
+  const seen = [];
+  class ChildProcess {
+    spawn(options) {
+      seen.push(options);
+    }
+  }
+  const rec = (...args) => seen.push(args);
+  return { seen, cp: { ChildProcess, spawnSync: rec, execFileSync: rec, execSync: rec } };
+}
+
+test("win32: async spawns and every sync form get windowsHide", () => {
+  const { seen, cp } = fakeCp();
+  install(cp, "win32");
+  install(cp, "win32"); // idempotent: no double wrap
+
+  new cp.ChildProcess().spawn({ file: "git", windowsHide: false });
+  cp.execFileSync("git", ["status"]);
+  cp.execFileSync("git", ["status"], { cwd: "x" });
+  cp.execFileSync("git", { cwd: "x" });
+  cp.execSync("dir");
+  cp.spawnSync("git", ["log"], undefined);
+
+  assert.deepEqual(seen, [
+    { file: "git", windowsHide: true },
+    ["git", ["status"], { windowsHide: true }],
+    ["git", ["status"], { cwd: "x", windowsHide: true }],
+    ["git", { cwd: "x", windowsHide: true }],
+    ["dir", { windowsHide: true }],
+    ["git", ["log"], { windowsHide: true }],
+  ]);
+});
+
+test("other platforms are left alone", () => {
+  const { cp } = fakeCp();
+  const before = { ...cp, spawn: cp.ChildProcess.prototype.spawn };
+  install(cp, "linux");
+  assert.equal(cp.execSync, before.execSync);
+  assert.equal(cp.ChildProcess.prototype.spawn, before.spawn);
+});