rename(#162): scrub remaining hm1nd references from comments and MCP instructions

All functional renames (MANAGER_NAME, MANAGER_AGENT → "root") were done in
earlier commits. This cleans up the stale `hm1nd` strings that remained in
doc comments, test fixture labels, and the manager MCP server instructions
(which told the manager its config lived at /agents/hm1nd/config/agent.nix).

hive-c0re/src/dashboard.rs

@@ -2561,7 +2561,7 @@ fn transient_label(k: crate::coordinator::TransientKind) -> &'static str {
 }
 
 /// Convert either a logical name or a container name back to the logical
-/// name. Sub-agents are `h-foo` → `foo`; manager stays `hm1nd`.
+/// name. Sub-agents are `h-foo` → `foo`; manager stays `root`.
 fn strip_container_prefix(name: &str) -> String {
     name.strip_prefix(lifecycle::AGENT_PREFIX)
         .unwrap_or(name)