ci: add Windows build to release workflow (NSIS .exe + MSI .msi)

[LocallyInsaneDB]

Summary

Adds a build-windows job to .github/workflows/release.yml so tagged releases automatically publish Windows installers alongside the existing macOS and Linux artifacts. No source changes — bundle.targets: "all" in src-tauri/tauri.conf.json already covers Windows targets; the job only needs to exist.

What ships per release after this

Asset	Produced by
Marky_<version>_x64-setup.exe	NSIS bundler (default Tauri 2 installer on Windows)
Marky_<version>_x64.msi	WiX MSI bundler

Naming follows the same Marky_<version>_<arch> convention as the existing Linux Marky_<version>_amd64.AppImage and macOS Marky_<version>_aarch64.tar.gz assets.

Implementation

• Runs on windows-latest — the GitHub-hosted image ships with MSVC 2022 Build Tools, the Windows SDK, and the WebView2 runtime, so no extra system-deps step is needed (unlike the Linux job).
• Mirrors the Linux job's step structure: Rust → pnpm → Node → pnpm install → pnpm tauri build → upload artifacts via gh release upload.
• Upload step uses shell: bash (Git Bash on the runner) so the find / cp / if [ -n ... ] pattern matches the Linux job verbatim — easier to maintain.
• WiX 3 is downloaded on demand by Tauri's bundler at build time; no extra setup step required.
• amd64 only — arm64 Windows runners (windows-11-arm) exist but are less stable; happy to add a matrix entry in a follow-up if you want it.

Why now

The Marky README lists Homebrew (macOS) and .deb (Ubuntu/Debian) install paths but no Windows entry. Forks/issues don't currently mention Windows, but the repo has a Tauri 2 setup that's a one-job addition away from full three-OS parity. I cross-compiled a working .exe locally via cargo-xwin from WSL to confirm the source tree is Windows-clean — this PR just adds the CI job to do the same thing the supported way on a native Windows runner.

Test plan

• CI: tag a test release (e.g. v0.1.3-test1) on a branch and confirm both *-setup.exe and *.msi appear in the GitHub release alongside the existing macOS/Linux assets.
• Install the .exe on a clean Windows 10/11 VM; launch via Start menu; open a .md file via the file picker.
• Install the .msi on the same VM (after uninstalling the NSIS build); confirm same behaviour.
• Confirm the existing macOS and Linux jobs still pass unchanged (the only diff to those jobs in this PR is the appended build-windows job at the bottom of the file).

Happy to iterate on artifact naming, add arm64, switch to tauri-apps/tauri-action for consistency with the macOS job, or anything else you'd prefer.