deploy: rename enableAllLocalDefaults to deploy.singleHostSwarm

Same defect as the switch below it, one tier up: it sat at the TOP of
`services.hyperhive`, a namespace that is meant to be everything about
hyperhive rather than the settings of a single hive. Whether this box is
the whole deployment is as per-host as a decision gets.

The name follows mara's sentence for what it means — "everything in the
swarm is running on this host" — rather than naming its mechanism.
"Defaults" was doing no work: it is not a defaults toggle, it is a claim
about where the swarm lives, and the pair now reads as the containment it
already was, singleHostSwarm implying allSwarmServices plus this hive.

One site was a setter rather than a reference: module-eval's `allLocal`
fixture passes an attrset merged into `services.hyperhive`, so its key
carries the path and had to become `deploy.singleHostSwarm`. A rename by
bare identifier is right for the twelve prose mentions and wrong for
exactly this one, which is worth knowing before the next rename.

nix/host-modules/deploy.nix

@@ -119,6 +119,16 @@ in
       [ "services" "hyperhive" "swarm" "enableRequiredServices" ]
       [ "services" "hyperhive" "deploy" "allSwarmServices" ]
     )
+
+    # The mode above that one. It sat at the TOP of `services.hyperhive`,
+    # which is the same defect one tier up: that namespace is everything
+    # about hyperhive, not the settings of a single hive. The new name says
+    # what the mode asserts — the whole swarm runs on this host — instead of
+    # naming its mechanism.
+    (lib.mkRenamedOptionModule
+      [ "services" "hyperhive" "enableAllLocalDefaults" ]
+      [ "services" "hyperhive" "deploy" "singleHostSwarm" ]
+    )
   ];
 
   # ⚠️ `deploy.forgejo` is declared in ./hive-ci.nix, not here, and it is the