nix: comments state current behaviour, not history

Rewrite comments and option descriptions under nix/ that narrate how the
code got here ("used to", "new name", "sat at the TOP", "no longer",
renamed/moved narration, attributions) to say what the code does now and
why. Comments and description strings only; no logic changes.

Files in open PR #4970's diff are left alone. Refs #3902

nix/host-modules/hyperhive.nix

@@ -103,8 +103,8 @@ in
 
   # Where the swarm lives. Declared beside the hive's own identity
   # because it is what that identity is derived FROM — every hive in a
-  # swarm is a sub-domain of it. Unlike the renamed options nearby, this
-  # is genuinely new: nothing moved here, so there is no alias.
+  # swarm is a sub-domain of it. No alias: this option has no earlier
+  # spelling.
   options.services.hyperhive.swarm.domain = lib.mkOption {
     type = lib.types.nullOr lib.types.str;
     default = null;
@@ -145,7 +145,7 @@ in
       (`services.hyperhive.deploy.hive-controller.enable`,
       `deploy.bao.enable`, `deploy.matrix.enable`). Distinct from
       `services.hyperhive.domain` (the machine-addressable DNS name)
-      but no longer merely cosmetic: a hive occupies
+      and not merely cosmetic: a hive occupies
       `<hiveName>.<swarm.domain>`, so this is the label the hive is
       *addressed* by as well as the one it is called. Exposed to
       agents as `HYPERHIVE_HIVE_NAME`; surfaced in the dashboard