fix(desktop): anchor Windows update handoff cwd

[hungjoong]

Summary

• set the Windows Desktop hand-off working directory to InstallRoot before running the updater and post-update verifier
• prevent verify_windows_desktop_update(Path.cwd()) from searching below the packaged Electron directory and falsely reporting Hermes.exe missing
• add a regression check for the hand-off cwd anchor

Validation

• npm --workspace apps/desktop test -- electron/update-handoff-marker.test.ts
• PowerShell script parse check

Observed on Windows: the Desktop update completed and relaunched successfully, but the detached updater inherited a non-checkout working directory, causing a false verification failure.

[alt-glitch]

This was generated by AI during triage.

Related: #105599 (earlier fix for the same false post-update verification failure, passes the checkout root to the verify step) and #106007 (same approach as #105599). This PR instead anchors the hand-off cwd with Set-Location -LiteralPath $InstallRoot in windows.ps1. Competing fixes for #106097 / #105587; flagging so a maintainer can pick one mechanism.

[teknium1]

Resolved on main by #106175 (c32e0ac), salvaging @fangliquanflq’s earlier #105168 with authorship preserved. The handoff now sets the native process cwd to InstallRoot before launching update/verification children, retaining all integrity checks. Native Windows regression coverage exercises the production call: neutralizing it reproduces the wrong cwd; restoring it passes all 15 related tests. Receipt: https://github.com/NousResearch/hermes-agent/actions/runs/34293439570. Thanks @hungjoong for the fix and investigation. Closing this superseded proposal to consolidate the resolved cwd bug.