docs: name the matrix host options by their new path

Every prose and error-message reference to the moved options, including
two in hive-c0re/src/matrix.rs that omitted the services. prefix and so
read as the per-agent option. An error that names an option the operator
cannot find is worse than no hint.

docs/matrix.md

@@ -3,7 +3,7 @@
 Private Matrix homeserver (matrix-tuwunel — the conduwuit
 successor) wrapped in a nixos-container, plus optional fluffychat-web
 client at `matrix.<hive>/`. Configured via
-`services.hyperhive.matrix.*`; vhost routing lives in
+`services.hyperhive.swarm.matrix.*`; vhost routing lives in
 [`gateway.md`](gateway.md).
 
 ## Container shape
@@ -60,7 +60,7 @@ client needs to reach the client-server API directly.
 
 **Breaking change**: used to default to `true`. Operators relying on
 external reach must add
-`services.hyperhive.matrix.openFirewall = true;` before rebuilding.
+`services.hyperhive.swarm.matrix.openFirewall = true;` before rebuilding.
 
 Federation port 8448 is intentionally not opened here — tuwunel
 serves the federation API on the same `httpPort` as client-server
@@ -119,7 +119,7 @@ Initial rollout settings:
   `yes_i_am_very_very_sure_…_open_registration_…` flag keeps the
   server closed to anyone without the token.
 - `allow_encryption` — server-side E2EE switch, sourced from
-  `services.hyperhive.matrix.allowEncryption` (**default `false`**, opt-in).
+  `services.hyperhive.swarm.matrix.allowEncryption` (**default `false`**, opt-in).
   Off by default because on the hive-internal homeserver the operator
   already controls the transport; turn it on for encrypted rooms on
   external / federated homeservers or to keep contents opaque to the
@@ -168,7 +168,7 @@ re-creation (e.g. after a homeserver wipe).
 ## Configuration tuning
 
 ```nix
-services.hyperhive.matrix = {
+services.hyperhive.swarm.matrix = {
   trustedServers  = [ "matrix.org" "example.com" ];   # default: []
   maxRequestSize  = 20000000;                          # default: 20 MB
 };