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).

docs/process/conventions.md

@@ -11,7 +11,7 @@ exist because something already went wrong without them.
 - `MAX_AGENT_NAME` in `hive-c0re/src/lifecycle/mod.rs` enforces the cap.
 - Per-agent web UI port = `WEB_PORT_BASE + FNV1a(name) % WEB_PORT_RANGE`
   (8100..8999) for every agent; dashboard
-  `services.hyperhive.c0re.dashboardPort` (default 7000).
+  `services.hyperhive.swarm.dashboardPort` (default 7000).
 
 ## Hive identity (label + domain + display names)