refactor(#2439): build hive-wide stop/start/restart DAGs dynamically

Hive-wide `stop` / `start` / `restart` emit ONE DAG with a per-agent
subgraph each (concurrent on their own leases) instead of N DAGs — and each
subgraph is now built dynamically from the agent's live running state rather
than a fixed template shape:

- online agent: the full stop→reconcile (restart: stop-for-update→reconcile)
  chain; `graceful` prepends signal→drain.
- offline agent: just `SetWanted → Reconcile` (nothing to quiesce/stop; a
  restart of a down agent is really a start).

The head `SetWanted` (intent) and tail `Reconcile` (convergence guarantee)
are always present; only the mechanical `Signal`/`Drain`/`StopForUpdate`
nodes are state-conditional. Keeping `Reconcile` in every shape closes the
TOCTOU window — a race-up between the `is_running` read and node exec is
still converged in-DAG (with `StopForUpdate`-noop as the backstop) — with no
reliance on an external reconcile sweep.

The state-aware assembly needs an async `is_running` read, so it moves out
of the pure/sync `templates.rs` into `submit.rs`, layered as pure
`*_chain(running)` → pure `*_spec(targets)` (the unit-test seam) → async
`*_many` (reads live state + submits). `templates.rs` keeps only the shared
pure primitives (`node`/`after_ok`/`rebuild_nodes`).

Callers await the now-async submit fns (server, dashboard, socket_server).
Tests exercise both the online and offline shapes via the pure `*_spec`
seam. docs/coordinator.md shapes updated.

hive-c0re/src/socket_server/lifecycle_handlers.rs

@@ -12,7 +12,11 @@ use crate::coordinator::Coordinator;
 
 /// `Start` — start a container, kicking its next turn. The caller must be an
 /// ancestor of `name` in the topology (the root covers every agent).
-pub(super) fn handle_start(coord: &Arc<Coordinator>, agent: &str, name: &str) -> AgentResponse {
+pub(super) async fn handle_start(
+    coord: &Arc<Coordinator>,
+    agent: &str,
+    name: &str,
+) -> AgentResponse {
     if let Some(err) = require_descendant(agent, name, "start") {
         return err;
     }
@@ -25,7 +29,8 @@ pub(super) fn handle_start(coord: &Arc<Coordinator>, agent: &str, name: &str) ->
         name,
         crate::job_queue::Source::Manual,
         format!("agent `{agent}` start tool"),
-    );
+    )
+    .await;
     AgentResponse::Ok
 }
 
@@ -56,7 +61,8 @@ pub(super) async fn handle_restart(
         name,
         crate::job_queue::Source::Manual,
         format!("agent `{agent}` restart tool"),
-    );
+    )
+    .await;
     AgentResponse::Ok
 }
 

hive-c0re/src/socket_server/mod.rs

@@ -557,7 +557,7 @@ async fn dispatch(req: &AgentRequest, agent: &str, coord: &Arc<Coordinator>) ->
     match req {
         // Lifecycle + config: caller must be an ancestor of the target
         // (a parent owns its whole subtree; the root covers every agent).
-        AgentRequest::Start { name } => handle_start(coord, agent, name),
+        AgentRequest::Start { name } => handle_start(coord, agent, name).await,
         AgentRequest::Restart { name } => handle_restart(coord, agent, name).await,
         AgentRequest::Kill { name } => handle_kill(coord, agent, name).await,
         AgentRequest::Update { name } => handle_update(coord, agent, name),