chore: import upstream snapshot with attribution

doc/devdocs/processes/update-process.md

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+# PowerToys Update Process
+
+This document describes how the PowerToys update mechanism works.
+
+## Key Files
+
+- `updating.h` and `updating.cpp` in common - Contains code for handling updates and helper functions
+- `update_state.h` and `update_state.cpp` - Handles loading and saving of update state
+
+## Update Process
+
+### Version Detection
+- Uses GitHub API to get the latest version information
+- API returns JSON with release information including version and assets
+- Checks asset names to find the correct installer based on:
+  - Architecture (ARM64 or X64)
+  - Installation scope (user or machine)
+
+### Installation Scope
+- Differentiates between user installer and machine installer
+- Different patterns are defined to distinguish between the two scopes
+- Both have different upgrade codes
+
+### Update State
+- State is stored in a local file
+- Contains information like:
+  - Current update state
+  - Release page URL
+  - Last time check was performed
+  - Whether a new version is available
+  - Whether installer is already downloaded
+
+### Update Checking
+- Manual check: When user clicks "Check for Updates" in settings
+- Automatic check: Periodic update worker runs periodically to check for updates
+- Update state is saved to: `%LOCALAPPDATA%\Microsoft\PowerToys\update_state.json`
+
+### Update Process Flow
+1. Check current version against latest version from GitHub
+2. If newer version exists:
+   - Check metered connection settings
+   - Check if automatic updates are enabled
+   - Check GPO settings
+3. Process new version:
+   - Check if installer is already downloaded
+   - Clean up old installer files
+   - Download new installer if needed
+4. Notify user via toast notification
+
+### PowerToys Updater
+- `PowerToysUpdate.exe` - Executable shipped with installer
+- Handles downloading and running the installer
+- Called when user clicks the update toast notification
+- Downloads the installer if not already downloaded
+
+### Version Numbering
+- Semantic versioning: `MAJOR.MINOR.PATCH`
+- MINOR version increases with regular releases (e.g., 0.89.0)
+- PATCH version increases for hotfixes (e.g., 0.87.0 → 0.87.1)
+
+### Installer Details
+- Uses WiX bootstrapper
+- Defines upgrade codes for per-user and per-machine installations
+- These codes must remain consistent for proper updating
+
+## GPO Update Settings
+
+PowerToys respects Group Policy settings for controlling updates:
+
+- `disable automatic update download` - Prevents automatic downloading
+- `disable new update toast` - Controls if toast notifications are shown
+- `suspend new update toast` - Suspends toast notifications for 2 minor releases
+
+## User Settings
+
+Users can control update behavior through the PowerToys settings:
+
+- Automatic update downloads can be enabled/disabled
+- Download and install updates automatically on metered connections
+
+## Update Notification
+
+When a new update is available:
+1. Toast notification appears in the Windows Action Center
+2. Clicking the notification starts the update process
+3. The updater downloads the installer (if not already downloaded)
+4. The installer runs with appropriate command-line arguments
+
+## Debugging Tips
+
+### Testing Update Detection
+- To force an update check, modify the timestamp in the update state file to an earlier date
+- Exit PowerToys, modify the file, then restart PowerToys
+
+### Common Issues
+- Permission issues can prevent downloading updates
+- Network connectivity problems may interrupt downloads
+- Group Policy settings may block updates
+- Installer may fail if the application is running
+
+### Update Logs
+- Check PowerToys logs for update-related messages
+- `%LOCALAPPDATA%\Microsoft\PowerToys\Logs\PowerToys-*.log`
+- Look for entries related to update checking and downloading
+
+## Rollout Considerations
+
+- Updates are made available to all users simultaneously
+- No staged rollout mechanism is currently implemented
+- Critical issues discovered after release require a hotfix
+- See [Release Process](release-process.md) for details on creating hotfixes