server: notify manager on admin-socket Rebuild outcomes

HostRequest::Rebuild was the only rebuild path that bypassed
notify_manager. dashboard / auto_update / actions::approve
already emit Rebuilt events on both success + failure, but a
'hive-c0re rebuild <name>' from the host CLI (and the recent
matrix-flake build failure that surfaced in journald) left the
manager in the dark.

mirror auto_update::rebuild_agent's pattern: on success →
Rebuilt{ok:true}, on failure → Rebuilt{ok:false, note=
format!('{e:#}')}. note carries the stderr tail lifecycle::run
collected (the actual nix error: missing prompt file, dep
build failure, etc.), so the manager has enough context to
adjust the agent's agent.nix without ssh-ing to the host.

hive-c0re/src/server.rs

@@ -129,7 +129,7 @@ async fn dispatch(req: &HostRequest, coord: Arc<Coordinator>) -> HostResponse {
                 let applied_dir = Coordinator::agent_applied_dir(name);
                 let claude_dir = Coordinator::agent_claude_dir(name);
                 let notes_dir = Coordinator::agent_notes_dir(name);
-                lifecycle::rebuild(
+                let result = lifecycle::rebuild(
                     name,
                     &coord.hyperhive_flake,
                     &agent_dir,
@@ -139,7 +139,30 @@ async fn dispatch(req: &HostRequest, coord: Arc<Coordinator>) -> HostResponse {
                     coord.dashboard_port,
                     &coord.operator_pronouns,
                 )
-                .await?;
+                .await;
+                // Mirror auto_update::rebuild_agent — the manager wants
+                // to know about every rebuild attempt regardless of
+                // which surface triggered it, especially failures
+                // (build error → manager can adjust the agent's
+                // agent.nix). Without this the admin-socket CLI was
+                // a notify-gap.
+                match &result {
+                    Ok(()) => coord.notify_manager(&hive_sh4re::HelperEvent::Rebuilt {
+                        agent: name.clone(),
+                        ok: true,
+                        note: None,
+                        sha: None,
+                        tag: None,
+                    }),
+                    Err(e) => coord.notify_manager(&hive_sh4re::HelperEvent::Rebuilt {
+                        agent: name.clone(),
+                        ok: false,
+                        note: Some(format!("{e:#}")),
+                        sha: None,
+                        tag: None,
+                    }),
+                }
+                result?;
                 HostResponse::success()
             }
             HostRequest::List => HostResponse::list(lifecycle::list().await?),