refactor: unify AgentServer + ManagerServer into HiveServer {socket, flavor}

docs/conventions.md

@@ -311,10 +311,10 @@ from `tool-groups.json`). Unrecognised tokens are logged and skipped. Falls back
 to `ToolGroup::AGENT_DEFAULT` (`messaging`, `meta`, `inbox`, `execution`) or
 `ToolGroup::MANAGER_DEFAULT` (all groups) when the var is absent or empty.
 
-**Updating the surface** — when a new `#[tool]` fn is added to `AgentServer`
-or `ManagerServer` in `hive-ag3nt/src/mcp.rs`, add its name to the matching
-`ToolGroup::tools()` slice in `hive-sh4re/src/lib.rs`. That's the single
-source of truth; `allowed_mcp_tools` reads it at session start.
+**Updating the surface** — when a new `#[tool]` fn is added to `HiveServer`
+in `hive-ag3nt/src/mcp.rs`, add its name to the matching `ToolGroup::tools()`
+slice in `hive-sh4re/src/lib.rs`. That's the single source of truth;
+`allowed_mcp_tools` reads it at session start.
 
 ## Capabilities
 

hive-c0re/src/agent_server.rs

@@ -345,6 +345,29 @@ async fn dispatch(req: &AgentRequest, agent: &str, coord: &Arc<Coordinator>) ->
                 Err(message) => AgentResponse::Err { message },
             }
         }
+        AgentRequest::Start { name } => {
+            if !crate::topology::children_of(agent)
+                .iter()
+                .any(|c| c == name)
+            {
+                return AgentResponse::Err {
+                    message: format!(
+                        "agent `{agent}` cannot start `{name}`: \
+                         not a direct child in the topology tree"
+                    ),
+                };
+            }
+            tracing::info!(%agent, %name, "agent: start child");
+            match crate::lifecycle::start(name).await {
+                Ok(()) => {
+                    coord.kick_agent(name, "container started");
+                    AgentResponse::Ok
+                }
+                Err(e) => AgentResponse::Err {
+                    message: format!("{e:#}"),
+                },
+            }
+        }
         AgentRequest::Restart { name } => {
             // Topology check: the caller must be the direct parent of the
             // target. This is the only authorisation criterion — no