fix(nix): the rename lives with the module that declares the options

mara: "remove the extra deprecatios file, less comments". The alias now
sits in hive-forge/default.nix next to the options it renames, and the
comment is three lines instead of eighteen.

Better than tidier: there is no shared file for the sibling migrations
to queue behind. Matrix's rename goes in hive-matrix.nix, authelia's in
its own module, and none of them touch each other. hive-ci.nix declares
swarm.forge.ci.* from a different module and stays covered, because the
rename is on the namespace rather than on the declaring file.

Re-ran the check both ways this time, per argus on the last round: old
paths set and new paths read back 3999 / 7, and a config that only uses
the new paths produces no warnings at all.

nix/host-modules/default.nix

@@ -12,7 +12,6 @@
 {
   imports = [
     ./hyperhive.nix
-    ./swarm-renames.nix
     ./hive-c0re
     ./hive-ci.nix
     ./hive-forge

nix/host-modules/hive-forge/default.nix

@@ -82,6 +82,16 @@ in
   # (base URL), the same shape as the GitHub PAT / matrix extra-account
   # flows. See `hive-c0re/src/dashboard/extra_forges.rs`.
 
+  # Forge moved under `swarm` when the swarm-global services were
+  # consolidated. One rename for the namespace: the subtree comes with it,
+  # so existing hives keep evaluating and get one warning naming both paths.
+  imports = [
+    (lib.mkRenamedOptionModule
+      [ "services" "hyperhive" "forge" ]
+      [ "services" "hyperhive" "swarm" "forge" ]
+    )
+  ];
+
   # The internal forge is mandatory — it's the canonical store for the
   # meta flake + every agent's config repo (and the `internal/*` repos),
   # so there is no enable/disable toggle. It deploys whenever hyperhive

nix/host-modules/swarm-renames.nix

@@ -1,26 +0,0 @@
-# Backwards-compatibility aliases for options that moved under
-# `services.hyperhive.swarm.*` when the swarm-global services were
-# consolidated into one namespace.
-#
-# One rename per moved *namespace*, not per option: `mkRenamedOptionModule`
-# takes the attrset path and carries the whole subtree, nested children
-# included. An existing hive keeps evaluating, and its operator gets a single
-# warning naming both paths rather than one per option they had set.
-#
-# A per-leaf list would also work and would be strictly worse: every option
-# added under `swarm.forge` later would need remembering here to get an alias,
-# so the list is a thing that can silently fall behind the options it mirrors.
-#
-# ⚠️ Only options that are genuinely **swarm-global** belong here. The
-# per-agent `hyperhive.forge.url` (`nix/agent-modules/forge.nix`) is a client
-# pointer at whatever forge an agent talks to — it shares a word with the
-# service and nothing else, and it does not move.
-{ lib, ... }:
-{
-  imports = [
-    (lib.mkRenamedOptionModule
-      [ "services" "hyperhive" "forge" ]
-      [ "services" "hyperhive" "swarm" "forge" ]
-    )
-  ];
-}