hyperhive: make the values the meta-flake render reads swarm-wide

Five host options whose values hive-c0re renders into every agent's
build move under services.hyperhive.swarm, so the swarm states each of
them once instead of every hive carrying its own copy:

  c0re.dashboardPort          -> swarm.dashboardPort
  c0re.claudeCodePackage      -> swarm.claudeCodePackage
  github.enable               -> swarm.github.enable
  otel.collector.port         -> swarm.hiveOtel.collectorPort
  otel.extraResourceAttributes -> swarm.hiveOtel.extraResourceAttributes

Every old path is a mkRenamedOptionModule alias, so a host that sets one
keeps its value and gets an eval warning naming the new path. Types and
defaults are unchanged, so the rendered meta flake, serve.json and
hive-c0re's environment are the same as before on a host that sets
none of them.

The readers move with them: serve.json and its gc-root assertion, the
hive-c0re environment, the hive collector's listen address and bridge
port, the swarm collector's port-collision assertion, and the
claude-login and review-classifier containers' claude pin. The
swarm-services-switch fixture sets the swarm path and now also checks
that serve.json carries the pinned claude.

Part of #4857 (slice 2).

nix/host-modules/hive-gateway/options.nix

@@ -62,7 +62,7 @@ in
       description = ''
         TCP port the gateway proxies non-static requests to. Defaults
         to `7000` (hive-c0re's out-of-the-box dashboard port). Operators
-        who change `services.hyperhive.c0re.dashboardPort` should set
+        who change `services.hyperhive.swarm.dashboardPort` should set
         `upstreamPort` to match — kept as a hardcoded default rather
         than a cross-reference to keep this module's options eval
         independent of c0re's option tree shape.