Test builds: tool/dev_release.sh builds Linux here and publishes to a dev prerelease that dev builds update from

X.Y.Z-dev.N builds read the dev prerelease's manifest as well as the
stable one and take the newer, so a tester gets each test build through
the normal update and lands back on stable at the release.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/ARCHITECTURE.md

@@ -1144,7 +1144,11 @@ does the same from the app binary. In the app, `UpdateController`
 indicator, which opens the update card, and restarts the app ("Update and
 restart", closing Hive first).
 Settings has Check now and an auto-check toggle. The manifest is `updates/manifest.json` in
-this repo, written by `tool/release.sh`.
+this repo, written by `tool/release.sh`. Test builds (`X.Y.Z-dev.N`,
+`isDevBuild`) also read `devManifestUrl`, the `manifest.json` of the `dev`
+prerelease (`tool/dev_release.sh`), and take the newer of the two
+(`fetchLatestManifest`); the release X.Y.Z outranks its test builds, so
+testers land back on stable. `0.0.0-dev` (a dev run) checks nothing.
 
 ## Decisions