🤖 docs: add Windows installation instructions

- Add Windows installer exe to release builds list
- Add Windows installation steps
- Clarify that Windows builds are only available from releases (not dev builds)
- Fix typo: 'Down' -> 'Download'

Author: deansheather

docs/install.md

@@ -8,16 +8,19 @@ Download pre-built binaries from [the releases page](https://github.com/coder/mu
 
 - **macOS**: Signed and notarized DMG (separate builds for Intel/Apple Silicon)
 - **Linux**: AppImage
+- **Windows**: Installer exe
 
 ### Development Builds
 
-Down pre-built binaries of `main` from [GitHub Actions](https://github.com/coder/mux/actions/workflows/build.yml):
+Download pre-built binaries of `main` from [GitHub Actions](https://github.com/coder/mux/actions/workflows/build.yml):
 
 - **macOS**: Signed and notarized DMG
   - `macos-dmg-x64` (Intel Macs)
   - `macos-dmg-arm64` (Apple Silicon)
 - **Linux**: AppImage (portable, works on most distros)
 
+> **Note**: Windows builds are only available from [releases](https://github.com/coder/mux/releases), not from development builds.
+
 To download:
 
 1. Go to the [Build workflow](https://github.com/coder/mux/actions/workflows/build.yml?query=event:merge_group)
@@ -44,6 +47,13 @@ The app is code-signed and notarized by Apple, so it will open without security
 2. Make it executable: `chmod +x Mux-*.AppImage`
 3. Run it: `./Mux-*.AppImage`
 
+**Windows:**
+
+1. Download the installer exe from [releases](https://github.com/coder/mux/releases) (e.g., `mux-x.x.x-x64.exe`)
+2. Run the installer
+3. Follow the installation prompts
+4. Launch Mux from the Start menu or desktop shortcut
+
 ### Testing Pre-Release Builds
 
 ⚠️ **Note**: Only builds from the `main` branch are signed and notarized. If you're testing a build from a pull request or other branch, you'll need to bypass macOS Gatekeeper: