jobq-wire: name every outcome, keep the enum spellings, document the schema

Three things, all from review:

Accepted outcomes were built from a hand-listed [Done, Failed, Cancelled,
Skipped] array. Exhaustive today, silently short the day someone adds a
variant — the new outcome would vanish from every edge that accepts it.
BitFlags::ALL asks the type instead.

TerminalState carried rename_all = "snake_case" while its sibling State did
not, so one enum shipped "done" and the other "Done". A rename is a second
spelling of a name that then has to be kept in agreement by hand; both now
serialise their variant names verbatim. Nothing else reads TerminalState off
a wire, so no consumer moves. GraphDep's tag values likewise.

The endpoint documented its body as serde_json::Value, which tells a spec
reader nothing. hive-jobq-wire now derives ToSchema. State and TerminalState
are foreign types here and utoipa stays out of the scheduler crate, so the
schema points at local mirror enums. A mirror that drifts is worse than none:
the conversions are exhaustive (a new upstream variant fails the build) and a
test asserts each documented name equals the serialised one, since an
exhaustive match still compiles when only the spellings diverge.

hive-c0re/src/dashboard/state_snapshot.rs

@@ -660,9 +660,8 @@ fn build_approval_views(approvals: Vec<Approval>) -> Vec<ApprovalView> {
             dependency edges with their accepted-outcome sets, lifecycle, and \
             one opaque per-node payload. Group roots ride as ordinary nodes \
             (`parent: null`) and `Done` nodes are not filtered — a consumer \
-            renders the graph without knowing what any node means. Each element \
-            is a `hive_jobq_wire::GraphNode`",
-            body = serde_json::Value),
+            renders the graph without knowing what any node means.",
+            body = Vec<hive_jobq_wire::GraphNode>),
     ),
     tag = "state_snapshot"
 )]