[stuartd]

ClipDiff can now update through an unsigned per-user Inno Setup installer instead of manual ZIP replacement. Each native extension binary ships under its SHA-256 filename, so an update can replace the app while Explorer keeps an older DLL loaded. Setup closes ClipDiff gracefully, preserves preferences/startup registration, and offers relaunch. Loaded obsolete DLLs are retained and cleanup failures are nonfatal.

Add an Enable/Not now consent prompt, a tray toggle for daily background GitHub checks, and a manual Check for updates action. Newer releases produce one notification per version; Download opens the exact release page. No clipboard/document data is sent, and nothing is downloaded or installed automatically.

The installer and update-check implementations are in separate commits. Release CI builds the installer alongside both portable ZIPs. Old pre-installer portable builds need a one-time manual quit when migrating; subsequent installer upgrades close the app automatically.

Validation passed on Windows at 742a906:

• 96 core tests, 330 Windows tests, and 37 update/deployment tests.
• Native Shell menu discovery, COM activation/delivery, selection visibility and lifecycle tests.
• Installer first install, running-app upgrades with unchanged and changed loaded DLLs, prerelease installer compilation/upgrade, and uninstall, without a restart.
• Release tag/version propagation and validated portable payloads/ZIPs.

Successful Windows run · Download unsigned installer artifact

Keep this draft pending the interactive Explorer/menu caching, consent UI and real network checks in the Windows checklist. CI holds DLLs open with LoadLibrary; actual Explorer interaction still needs desktop verification.

Closes #27.
Closes #25.