Drop SilverBullet + the task/calendar Hermes skills

modules/builder.nix

@@ -71,7 +71,6 @@ let
     homelab-garage
     homelab-notes
     homelab-hermes
-    homelab-silverbullet
 
     # Observability stack (server + VPN gated on "observability-server",
     # sender gated on "observability-sender").
@@ -141,9 +140,10 @@ let
         (noughtyHostModule name entry)
         # Record the git revision this config was built from, so every host
         # reports it via `nixos-version --configuration-revision` and (via
-        # the observability-sender textfile metric) into Mimir -- that's how
-        # cc-sync detects merged-but-not-deployed hosts. Dirty trees get the
-        # "<rev>-dirty" pseudo-rev (or null on nix without dirtyRev).
+        # the observability-sender textfile metric) into Mimir -- i.e. which
+        # rev each host actually runs, so a merged-but-not-deployed host is
+        # visible without ssh. Dirty trees get the "<rev>-dirty" pseudo-rev
+        # (or null on nix without dirtyRev).
         { system.configurationRevision = self.rev or self.dirtyRev or null; }
       ]
       ++ hmNixosBase