swarm: move the matrix packages to deploy, where their enable already lives

Which build a service runs is a decision of the host that runs it, so
`*.package` belongs with `enable` rather than in the namespace every hive
must agree on byte for byte.

The `gui` pair was the sharpest case and the reason this starts here:
`gui.enable` moved to `deploy.*` in an earlier slice while `gui.package`
stayed behind, so one web client's two halves sat in two namespaces —
and hive-matrix.nix said so, in a comment directly above the option.
The diff removes a stated inconsistency rather than introducing a rule.

Both old paths keep working through `mkRenamedOptionModule`; both are
settable (neither is `readOnly`), so both get a shim. The `matrixOldPath`
fixture in module-eval.nix now sets eight options through their
pre-rename paths instead of six, so dropping either new shim fails the
eval rather than silently dropping a definition.

Prose swept in the same commit: three comments claimed the package was
swarm-wide or named the pre-rename path, and docs/web-ui/dashboard.md
named `swarm.matrix.gui.package` two lines above
`deploy.matrix.gui.enable` — the same asymmetry this commit exists to
remove, displayed in the docs. A shim keeps the old spelling valid, so
no build, lint or broken-reference search would have found that line.

Refs #3772.

nix/host-modules/deploy.nix

@@ -335,6 +335,20 @@ in
       [ "services" "hyperhive" "swarm" "wireguard" "persistentKeepalive" ]
       [ "services" "hyperhive" "deploy" "wireguard" "persistentKeepalive" ]
     )
+
+    # Which build a service runs is a decision of the host that runs it, so
+    # every `*.package` follows its `enable` across. The split these replace
+    # was the sharpest case: `gui.enable` had already moved while
+    # `gui.package` stayed, so one client's two halves sat in two namespaces
+    # and ./hive-matrix.nix said so in a comment above the option.
+    (lib.mkRenamedOptionModule
+      [ "services" "hyperhive" "swarm" "matrix" "package" ]
+      [ "services" "hyperhive" "deploy" "matrix" "package" ]
+    )
+    (lib.mkRenamedOptionModule
+      [ "services" "hyperhive" "swarm" "matrix" "gui" "package" ]
+      [ "services" "hyperhive" "deploy" "matrix" "gui" "package" ]
+    )
   ];
 
   # ⚠️ `deploy.forgejo` is declared in ./hive-ci.nix, not here, and it is the