refactor: rename templates to agent.nix/ruth.nix, sweep stale name refs

nix/templates/harness/agent-service.nix

@@ -52,7 +52,7 @@ in
       these models instead of a hardcoded set.
 
       Configure hive-wide by setting a shared default (e.g. in your
-      `agent-base.nix`) or per-agent to narrow the menu — for example a
+      `agent.nix` shared defaults) or per-agent to narrow the menu — for example a
       haiku-only agent can hide `opus` and `sonnet`. The *current* model is
       still set by `hyperhive.model` and remains switchable at runtime via the
       UI; this option only controls which choices the picker presents.

nix/templates/harness/default.nix

@@ -1,5 +1,5 @@
 # Shared scaffolding for every hyperhive harness container.
-# `../agent-base.nix` and `../manager.nix` both import this; all
+# `../agent.nix` and `../ruth.nix` both import this; all
 # agents use the same service unit regardless of which entry-point
 # they came from.
 #

nix/templates/harness/docs.nix

@@ -15,7 +15,7 @@
     `$HIVE_DOCS_DIR/`, and appends a single pointer sentence to the agent's
     system prompt so it knows the docs exist (see
     `hive-ag3nt::prompt::render`). Default-on for the root/manager agent
-    (see `../manager.nix`), off elsewhere; any agent can flip it from its
+    (see `../ruth.nix`), off elsewhere; any agent can flip it from its
     `agent.nix`.
   '';