refactor(#2591): fix wire-shape consumers (server await_dags, tests)

- server::await_dags: a DAG is settled when gone from the snapshot (fully
  Done) or present with all nodes terminal; pending only with a non-terminal
  node (DagView no longer carries a rolled-up state).
- DagView::rollup_state() added to hive-sh4re — the shared node-set roll-up
  derivation every Rust consumer uses.
- JobQueue::build_log_id_of(node_id) — the node_id -> build_logs lookup the
  query endpoint will use; tests assert log-id via it now.
- tests: derive roll-up state; drop the off-wire step/build_log_id wire asserts.

hive-sh4re/src/jobs.rs

@@ -142,3 +142,37 @@ pub struct DagView {
     /// lingers until aged out by the history cap.
     pub nodes: Vec<NodeView>,
 }
+
+impl DagView {
+    /// Roll-up state derived from the node set — the shared derivation every
+    /// Rust consumer (hivectl, the wait loops, tests) uses so the dashboard's
+    /// JS render and the host agree: `Failed` if any node failed, else
+    /// `Running` if any running, else `Queued` if any queued, else
+    /// `Cancelled` if any cancelled, else `Done`. `Done` nodes are excluded
+    /// from the wire, so a DAG that is *entirely* done isn't sent at all —
+    /// its absence from the snapshot is what signals completion.
+    #[must_use]
+    pub fn rollup_state(&self) -> State {
+        let mut any_running = false;
+        let mut any_queued = false;
+        let mut any_cancelled = false;
+        for n in &self.nodes {
+            match n.state {
+                State::Failed => return State::Failed,
+                State::Running => any_running = true,
+                State::Queued => any_queued = true,
+                State::Cancelled => any_cancelled = true,
+                State::Done => {}
+            }
+        }
+        if any_running {
+            State::Running
+        } else if any_queued {
+            State::Queued
+        } else if any_cancelled {
+            State::Cancelled
+        } else {
+            State::Done
+        }
+    }
+}