An instance's factorio.version can now target a release channel such as
"stable" or "experimental" (any key from factorio.com/api/latest-releases)
in addition to "latest" and specific X.Y / X.Y.Z versions.
The controller proxies the latest-releases API through a ValueCache and
persists the last successful response to latest-releases.json, serving that
copy when the API is unreachable. On instance start the host resolves a
channel to the concrete version it points to and feeds it into the existing
checkForUpdates/findVersion path, so a channel auto-installs and runs like a
pinned version. The version selector in the web UI lists the available
channels alongside "latest".
Also clarifies the host log/error when a newer version cannot be downloaded
automatically because the host uses a direct (single-version) Factorio
install rather than a versioned directory.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
