Three findings from the operator's review, all correct.
1. Two insert_job's. Graph::insert_job had no caller outside hive-jobq's
own tests -- production only ever went through Scheduler::insert_job.
It existed because the graph-level one got written first. Deleted; the
tests moved onto a Scheduler, which is where insertion belongs anyway.
2. insert_job was not atomic, and the previous commit made that worse: a
forward edge or forward parent surfaced mid-loop, leaving the nodes
before it in the graph, and resolve_wanted ran after every insert, so
an unknown handle failed once the whole job was already committed.
The module documented this under "Partial insertion" instead of fixing
it -- prose describing a hole is not a design.
All three are decidable from what the builder holds, so
check_declaration_order now runs before the first insert and the loop
indexes ids directly. A malformed job leaves the graph untouched.
What remains mid-insert is the graph's own rejection (out-of-group
dep, empty DepWhen); closing that needs a dry-run validate on Graph,
which is a separate change.
3. DagSpec no longer boxes its recipe: it is generic over the closure,
which travels from the template that built it straight into submit.
The box bought type inference, and paying for it costs annotations --
`|b: &Job|` at each declaration site (the field needs an HRTB, and an
unannotated closure binds one lifetime) and `+ use<>` on each
returning signature (or the opaque type captures the caller's borrows).
Erasure is still needed where several recipe shapes share one type:
the boxed Declare stays for the executor's append_subgraph, and a test
table uses an erase() helper.
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