feat(#2788): carry Skipped to the wire as its own state

A node ruled out by its own dependency edges settles `Skipped` host-side,
but the wire folded it into `Cancelled` and `dag_view` filtered it out
entirely, so a client never saw which branch a run didn't take. Post-#2785
that is not a rare shape: every approval DAG has two not-taken tails and
every rebuild has one, on the happy path as much as on failure.

`State` gains `Skipped`, and it counts as terminal — the wait loops in
hivectl's progress display and the daemon's dag-settled check decide
"finished" with `all(is_terminal)`, so omitting it would hang them on
essentially every DAG.

`dag_view` now emits skipped nodes but no longer lets them keep a DAG
alive. Serialization and completion were the same expression: a DAG left
the snapshot because its nodes had all been filtered away. Keeping skipped
nodes on the wire under that rule would pin every finished deploy in the
queue view forever, so the completion test is now its own flag.

`rollupState` in the dashboard gains the matching arm. It has no `done`
case — `done` is inferred by falling off the wire — so its trailing
`return 'queued'` catches anything it doesn't recognise, and a green
deploy would have read as permanently queued the moment the backend
started emitting the new state. The Rust and JS roll-ups have silently
disagreed before; they are edited together here and say so.

hivectl/src/dag_progress.rs

@@ -291,6 +291,9 @@ fn state_glyph(state: hive_host_sock::jobs::State) -> &'static str {
         hive_host_sock::jobs::State::Done => "✔",
         hive_host_sock::jobs::State::Failed => "✖",
         hive_host_sock::jobs::State::Cancelled => "⊘",
+        // Distinct from cancelled: nothing went wrong, this branch just
+        // wasn't the one the run took.
+        hive_host_sock::jobs::State::Skipped => "·",
     }
 }