docs(conventions): reframe stale 'the manager' as the root/bootstrap agent

The manager is no longer a structural role — root-ness is purely
topological (an agent with no parent). Reframe the naming + socket
lines that presented 'the manager' as a fixed coordinating agent,
while keeping the manager-flavour socket/protocol identifiers (those
still name live code).

docs/conventions.md

@@ -7,10 +7,10 @@ exist because something already went wrong without them.
 
 - Containers are length-bounded by `nixos-container` (≤ 11 chars).
 - Sub-agents are `h-<name>` with `<name>` ≤ 9 chars.
-- The manager is `ruth` (fixed name).
+- One agent is the bootstrap/root container, with a fixed name (`ruth` today).
 - `MAX_AGENT_NAME` in `lifecycle.rs` enforces the cap.
 - Per-agent web UI port = `WEB_PORT_BASE + FNV1a(name) % WEB_PORT_RANGE`
-  (8100..8999) for every agent including the manager; dashboard
+  (8100..8999) for every agent including the bootstrap/root container; dashboard
   `cfg.dashboardPort` (default 7000).
 
 ## Hive identity (label + domain + display names)
@@ -56,8 +56,8 @@ peer's name when the caller knows it's hive-local.
 There are no auth tokens on the per-agent unix sockets. The socket
 *path* identifies the principal; perms come from "who has the
 bind-mount." A sub-agent only sees its own `/run/hive/mcp.sock`; the
-manager has access to its privileged socket; hive-c0re owns the host
-admin socket.
+root agent additionally has access to its privileged (manager-flavour)
+socket; hive-c0re owns the host admin socket.
 
 ### Wake injection