Updates from Gitea, step 5: the daily check's announcement, the docs, ADR 0009

The announcement was cut at the notification's 48 bytes; it now reads
"v0.11.0 is out: see Settings > Firmware". README: Updates from Gitea
and its limits. ADR 0009: the device trusts the two ISRG roots. R1.md:
what was built and the checks on the device, with what wasn't checked.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EhqxQ49eCju4CzKYNjZzwT

src/services/update_service.cpp

@@ -285,7 +285,7 @@ void UpdateService::serve() {
             if (r == Request::BackgroundCheck && gitea_.latest(latest) &&
                 release::shouldAnnounce(latest, runningVersion(), failedVersion(), announced_)) {
                 announced_ = latest.tag;
-                notify("Update " + latest.tag + " available: see Settings > Firmware", NotificationLevel::Info);
+                notify(latest.tag + " is out: see Settings > Firmware", NotificationLevel::Info);  // 48 bytes at most
             }
             break;
         }
@@ -307,7 +307,7 @@ void UpdateService::serve() {
     }
     // A check or a list someone asked for that failed says so; the daily one stays quiet.
     if ((r == Request::Check || r == Request::List) && gitea_.status() == GiteaReleases::Status::Failed)
-        notify("Releases: " + gitea_.error(), NotificationLevel::Warning);
+        notify(gitea_.error(), NotificationLevel::Warning);
     // IRC comes back, unless the device is about to restart into an update.
     if (held_ && phase_ != Phase::Installed && holdMemory) holdMemory(false);
     held_ = false;