Ship Cortext Desktop for Windows

## Goal

Cortext Desktop is currently limited to macOS. Bring the same local workspace to Windows without asking users to install or configure WordPress themselves.

## Tasks

- [ ] Build a Windows application and installer from the existing Desktop code, including the bundled runtime and Cortext plugin.
- [ ] Adapt process management, filesystem locations, ports, and first-launch setup to Windows while keeping workspace data outside replaceable application files.
- [ ] Preserve the workspace across application restarts, upgrades, repairs, and normal uninstall flows.
- [ ] Add Windows code signing, release artifacts, checksums, and update-channel support to the release process.

## Acceptance criteria

- A user can install Cortext Desktop on a supported Windows system without installing WordPress, PHP, or a database separately.
- First launch creates and opens a working local workspace.
- Pages and collections remain available after restarting and updating the application.
- The release process produces a signed installer and checksum through the normal Cortext release workflow.

Start by locating the existing Desktop code and the normal Cortext release workflow. Map the platform-specific process management, filesystem, ports, first-launch setup, installer, signing, and update steps before implementation. Done means a supported Windows user can install and launch a self-contained workspace, preserve data through restarts and upgrades, and receive signed release artifacts with checksums.

Written by the indexing model from the issue text.