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).

hive-c0re/src/coordinator.rs

@@ -54,7 +54,7 @@ pub struct Coordinator {
     pub nixpkgs_flake: String,
     /// Store path of the `claude-code` build every agent runs, written
     /// into each per-agent flake as `services.hyperhive.agent.claudeCodePath`. Set by
-    /// the NixOS module option `services.hyperhive.c0re.claudeCodePackage`
+    /// the NixOS module option `services.hyperhive.swarm.claudeCodePackage`
     /// (which resolves the package and hands us its path). `None` = every
     /// agent keeps the `claude-code` from its own nixpkgs.
     ///