Implements the Hazel/Squirrel-style update endpoint expected by the
Hyper Electron app (and the custom Linux updater).
- Endpoint at /api/update-check and /update
- Accepts query params: version, platform (or os), arch, channel
- Returns 204 or the classic {name, notes, pub_date, url?} JSON
- Supports explicit channel=canary so stable-installed clients can opt in
- Updated Release model to carry TagName and PublishedAt for proper responses
This pairs with the corresponding client change in the hyper repo
(branch: update-endpoint-quine).
