jobq: a job asks for the ids it wants back

The operator's instruction on the issue was "the closure returns an array
of guids, and enqueue_job returns the node ids in that order". What was
here instead returned a HashMap of everything inserted, and no caller used
the keys: submit dropped the return, insert_group did into_values(), and
the scheduler ignored what append_subgraph handed back. The guid-keyed
lookup was dead weight, and into_values() made that Vec arbitrarily
ordered -- harmless only because nothing read it.

insert_job now takes FnOnce(&JobBuilder) -> Vec<NodeGuid> and returns the
matching ids positionally. A handle from another job is UnknownNode rather
than a silent omission: the return is positional, so a short vector would
misalign every id after it.

c0re's Declare stays FnOnce(&Job) and the wrapper names no handles in one
place, rather than ending seven templates in an empty vector -- a DAG is
addressed by its container node, which submit inserts itself. That frees
insert_group from needing every id, so the node_rt pre-seeding goes too:
NodeRuntime is one Option field and every reader already tolerated a
missing entry (entry().or_default(), get().and_then(), iter().find()).

The tests are the argument for the shape: capturing a handle through a
mutable binding to look it up in the map afterwards collapses into
returning it and destructuring the result.

hive-c0re/src/job_queue/tests.rs

@@ -1252,12 +1252,11 @@ fn deploy_apply_grows_rebuild_subgraph_and_finalizes_after_it() {
     // BEFORE the emitting node is completed. Completing first would settle the
     // apply node `Done` with nothing under it, opening the tail's `AfterAny`
     // gate immediately and letting the deploy "finish" before it had built.
-    let grown = q.append_subgraph(
+    q.append_subgraph(
         id,
         templates::deploy_rebuild_nodes("agent-a", 11),
         apply.node_id,
     );
-    assert!(!grown.is_empty(), "subgraph grafted onto the apply node");
     q.complete_node(apply.node_id, Ok(()));
 
     // The grafted chain runs in rebuild order. `claim_one` asserts exactly one