hive-host-sock: a jobq graph wire type that doesn't know what a node is

`jobs::NodeView` can only ever display hive-c0re's queue. Five of its
fields are domain knowledge: `approval_id` is only ever on a
`DeployWindow`, `inputs` only on a `MetaLock`, `build_log_id` only on the
nix-heavy kinds, `agent` is derived from the payload, and `kind` is a
payload tag consumers branch on. A component built against that shape
cannot render a second jobq.

`graph::GraphNode` is `hive_jobq::Node` with both generics erased: the
crate's own field set, with everything domain-specific in one opaque
`payload.data` slot the consumer renders without branching on. That is
the crate boundary made visible — hive-jobq owns structure, its host owns
meaning — and it is the same split #2957 drew inside the code.

Two details that are easy to get wrong and are pinned by tests:

`GraphDep::Node` carries `accepts` as the **set** of terminal outcomes,
not a strong/weak flag. A template emits its tails as a pair edged on the
same upstream node, and the only thing telling them apart is which
outcomes each accepts; collapsing that renders two structurally different
nodes identically.

There is **no roll-up field**. A group root ships as an ordinary node
with `parent: None`, and its own `state` is its subtree's answer —
`Finishing` means "own logic done, children still running", the terminal
states are the rolled-up outcome. A separate field would be a lossier
copy: `DagView::rollup_state` flattens `Running` and `Finishing` into
one, which is exactly the distinction a viewer wants.

`State` and `TerminalState` are re-exported from `hive-jobq` rather than
redeclared, so they cannot drift from the scheduler that produces them.

Cargo.lock

@@ -1727,6 +1727,7 @@ dependencies = [
  "hive-sh4re",
  "hive-types",
  "serde",
+ "serde_json",
 ]
 
 [[package]]

hive-host-sock/Cargo.toml

@@ -13,3 +13,4 @@ hive-jobq.workspace = true
 hive-sh4re.workspace = true
 hive-types.workspace = true
 serde.workspace = true
+serde_json.workspace = true

hive-host-sock/src/graph.rs

@@ -0,0 +1,192 @@
+//! Generic jobq graph wire types — a `hive_jobq` graph serialised without
+//! knowing what its nodes mean.
+//!
+//! [`super::jobs`]'s `DagView` / `NodeView` are hive-c0re's *domain*
+//! projection: they carry `approval_id`, `inputs`, `build_log_id` and an
+//! `agent`, each meaningful for a subset of one specific node kind. Anything
+//! built on those can only ever display hive-c0re's queue.
+//!
+//! These types carry what `hive_jobq::Node` itself carries — identity, the
+//! parent tree, dependency edges, lifecycle — and push everything
+//! domain-specific into one opaque [`NodePayload::data`] slot the consumer
+//! renders without branching on. That is the crate boundary made visible:
+//! `hive-jobq` owns structure, its host owns meaning.
+//!
+//! There is deliberately **no roll-up field**. A group root's own [`State`]
+//! *is* its subtree's answer: `Finishing` means "own logic done, children
+//! still running", and the terminal states are the rolled-up outcome. A
+//! separate field would be a lossier copy of a value already on the wire —
+//! lossier because it would have to flatten `Running` and `Finishing` together.
+
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+
+pub use hive_jobq::{State, TerminalState};
+
+/// Node id, carried verbatim from `hive_jobq::NodeId`: globally unique across
+/// the whole graph, not per group. Opaque to consumers — they group by
+/// [`GraphNode::parent`] and match dependency edges, nothing more.
+pub type NodeId = u64;
+
+/// One node, serialised near-raw from `hive_jobq::Node`.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct GraphNode {
+    pub id: NodeId,
+    /// Structural parent, or `None` for a group root.
+    ///
+    /// A group root is an **ordinary node here** — nothing is hidden, so a
+    /// consumer needs no special case for "the container", and the root's
+    /// own `state` answers "how is this whole group doing".
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub parent: Option<NodeId>,
+    pub state: State,
+    #[serde(default, skip_serializing_if = "Vec::is_empty")]
+    pub deps: Vec<GraphDep>,
+    /// When the node entered `Running`. `None` until it starts; a node that
+    /// never ran keeps `None`.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub started_at: Option<DateTime<Utc>>,
+    /// When the node reached a terminal state. `None` while non-terminal.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub finished_at: Option<DateTime<Utc>>,
+    /// Failure reason, set only when this node's *own* logic failed — a node
+    /// that rolled up `Failed` from a child carries none of its own.
+    #[serde(default, skip_serializing_if = "Option::is_none")]
+    pub error: Option<String>,
+    pub payload: NodePayload,
+}
+
+/// What a node *is*, in terms the graph layer does not interpret.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct NodePayload {
+    /// Short tag the consumer displays verbatim. **Not** for matching on: a
+    /// generic viewer that branches on this has stopped being generic.
+    pub label: String,
+    /// Domain data, rendered generically (as key/value, a details pane, a
+    /// tooltip — the consumer's choice). Everything a specific host wants to
+    /// say about a node beyond its label lives here, so adding a field costs
+    /// the wire type nothing.
+    #[serde(default, skip_serializing_if = "serde_json::Value::is_null")]
+    pub data: serde_json::Value,
+}
+
+/// What must hold before a node runs.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case", tag = "kind")]
+pub enum GraphDep {
+    /// Depend on another node finishing acceptably.
+    Node {
+        /// The node depended on. May name a node the consumer has not been
+        /// sent (a filtered view); treat an absent target as satisfied.
+        id: NodeId,
+        /// **The outcomes that satisfy this edge, as a set** — not a
+        /// strong/weak flag.
+        ///
+        /// A template routinely emits several tails edged on the *same*
+        /// upstream node, distinguished only by which outcomes each accepts
+        /// (one for `Done`, one for `Failed`/`Cancelled`, …). Collapsing this
+        /// to a boolean renders those as identical nodes.
+        accepts: Vec<TerminalState>,
+    },
+    /// Need `count` units of a named resource. Named, not typed: the resource
+    /// vocabulary belongs to the host, so it rides as a string.
+    Resource { name: String, count: u32 },
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{GraphDep, GraphNode, NodePayload, State, TerminalState};
+
+    fn node(id: u64, parent: Option<u64>, state: State, deps: Vec<GraphDep>) -> GraphNode {
+        GraphNode {
+            id,
+            parent,
+            state,
+            deps,
+            started_at: None,
+            finished_at: None,
+            error: None,
+            payload: NodePayload {
+                label: "reconcile".to_owned(),
+                data: serde_json::Value::Null,
+            },
+        }
+    }
+
+    #[test]
+    fn a_node_round_trips_through_json() {
+        let before = node(
+            7,
+            Some(3),
+            State::Running,
+            vec![
+                GraphDep::Node {
+                    id: 3,
+                    accepts: vec![TerminalState::Done],
+                },
+                GraphDep::Resource {
+                    name: "build-slot".to_owned(),
+                    count: 1,
+                },
+            ],
+        );
+        let json = serde_json::to_string(&before).expect("serialises");
+        let after: GraphNode = serde_json::from_str(&json).expect("round trips");
+        assert_eq!(format!("{after:?}"), format!("{before:?}"));
+    }
+
+    #[test]
+    fn two_tails_on_one_upstream_are_distinguishable_by_their_accepted_set() {
+        // The reason `accepts` is a set and not a strong/weak bool: these two
+        // are the same shape and the same upstream, and *only* the outcome
+        // set tells them apart.
+        let ok_tail = node(
+            10,
+            None,
+            State::Pending,
+            vec![GraphDep::Node {
+                id: 4,
+                accepts: vec![TerminalState::Done],
+            }],
+        );
+        let fail_tail = node(
+            11,
+            None,
+            State::Pending,
+            vec![GraphDep::Node {
+                id: 4,
+                accepts: vec![TerminalState::Failed, TerminalState::Cancelled],
+            }],
+        );
+        let render = |n: &GraphNode| match n.deps.first() {
+            Some(GraphDep::Node { accepts, .. }) => format!("{accepts:?}"),
+            _ => "none".to_owned(),
+        };
+        assert_ne!(render(&ok_tail), render(&fail_tail));
+    }
+
+    #[test]
+    fn a_group_root_is_an_ordinary_node_and_carries_the_groups_answer() {
+        // No roll-up field: `Finishing` on the root says "own logic done,
+        // children still running", and a terminal root state is the roll-up.
+        let root = node(1, None, State::Finishing, Vec::new());
+        assert!(root.parent.is_none(), "a group root is just parentless");
+        assert_eq!(root.state, State::Finishing);
+
+        let done_root = node(2, None, State::Failed, Vec::new());
+        assert_eq!(
+            done_root.state,
+            State::Failed,
+            "the root's own state is the subtree's rolled-up outcome"
+        );
+    }
+
+    #[test]
+    fn an_empty_payload_slot_is_omitted_from_the_wire() {
+        // The opaque slot costs nothing when a host has nothing to say.
+        let json =
+            serde_json::to_string(&node(1, None, State::Pending, Vec::new())).expect("serialises");
+        assert!(!json.contains("\"data\""), "null data is skipped: {json}");
+        assert!(json.contains("\"label\""), "the label always rides: {json}");
+    }
+}

hive-host-sock/src/lib.rs

@@ -16,6 +16,7 @@ use hive_sh4re::{AgentStatusRow, Approval};
 use hive_types::Ident;
 use serde::{Deserialize, Serialize};
 
+pub mod graph;
 pub mod jobs;
 
 // ── Shared hive layout facts ──────────────────────────────────────────────