jobq-wire: move the generic graph projection into its own crate

The wire types were in hive-host-sock, which is the host *socket* crate — so
anything living there is core-shaped by construction, and the projection had
quietly grown two core dependencies to match: it selected roots by matching
NodeKind::Dag, and rendered payloads through free functions in hive-c0re that
nothing obliged a second host to write.

hive-jobq is the wrong home too. That crate is the scheduler — logic — and
folding presentation in means every consumer of it carries a JSON vocabulary
it may never serve.

So: a new hive-jobq-wire. A host implements WireNode for its payload N and
WireResource for its resource name R; GraphWire::wire_snapshot is
blanket-implemented for Graph<N, R> when both hold, and for nothing else. A
payload that has never said how it displays has no way onto the wire.

wire_snapshot takes the roots to serve rather than reading Graph::roots
itself. Nothing is ever removed from a Graph, so retention is a policy only
the host can hold; hive-c0re passes visible_roots(), which is the existing
MAX_HISTORY_DAGS bound selected structurally (a root is a node with no
parent) instead of by node kind.

hive-c0re/src/job_queue/resource.rs

@@ -58,15 +58,14 @@ pub enum Resource {
     MetaWindow,
 }
 
-impl Resource {
-    /// This resource's name on the generic graph wire.
-    ///
-    /// `hive_jobq` is generic over the resource type, so a viewer that can
-    /// render any graph gets a string here rather than this enum. The
-    /// `agent:` prefix keeps the per-agent leases from colliding with a
-    /// hypothetical global resource that happens to share an agent's name.
-    #[must_use]
-    pub fn wire_name(&self) -> String {
+/// This resource's name on the generic graph wire.
+///
+/// `hive_jobq` is generic over the resource type, so a viewer that can render
+/// any graph gets a string here rather than this enum. The `agent:` prefix
+/// keeps the per-agent leases from colliding with a hypothetical global
+/// resource that happens to share an agent's name.
+impl hive_jobq_wire::WireResource for Resource {
+    fn name(&self) -> String {
         match self {
             Resource::BuildSlot => "build-slot".to_owned(),
             Resource::Agent(agent) => format!("agent:{agent}"),