refactor(#2815): derive the transient pill from the running node

The dashboard pill was declared once per DAG at submit time, so a rebuild
reported `rebuilding` for its entire life — through the prebuild, the
stop, the swap, the tail and the reconcile. It named the intent of the
request, not what was happening.

It is now read off the nodes actually running. A node lights a pill when
it is `Running` and declares the agent's own resource. Declaring is the
test, not targeting: `Prebuild` and `MetaSync` name an agent but are
lease-exempt on purpose (the container keeps serving), so they must not
light one. It is also not the lease *owner* — `resource_state()` answers
"who holds the slot", which is a different question from "what is
running", and a descendant that borrows an ancestor's grant never
appears in that map.

`TransientKind` is gone entirely rather than being re-derived. The label
is the node's own wire tag (`NodeKind::as_str`) — the same vocabulary
`NodeView.kind` already ships, so a pill and a DAG node name an operation
identically and there is no second taxonomy to keep in step. Work with no
node behind it (destroy, migration) supplies its own literal.

`DagSpec::transient`, `Claim::transient`, `DagMeta::transient` and
`NodeKind::Dag`'s `transient` field all go with it.

## the safety half, which is deliberately not the display half

`crash_watch::is_deliberate_stop` used to match a `TransientKind` to
decide whether a vanished container was intentional or a crash. That made
a pill's display vocabulary decide an alerting question, so renaming or
adding a label would silently move the alerting boundary.

`TransientState` now carries two independent fields: `label` (rendered,
nothing branches on it) and `deliberate_stop` (read only by the crash
watcher). The producer sets the second, because the producer is the only
thing that knows — it is not recoverable from the first.

For queue work that value is `NodeKind::takes_container_down()`, and it
is emphatically not "holds a lease": `Create` and `Start` hold the
agent's lease exactly like `Stop` does, and a container dying *while
starting* is a real crash that must keep reporting as one. The default is
`false` on purpose — a wrong `false` costs a spurious crash event, a
wrong `true` swallows a real crash silently.

## known cost, accepted on the issue

A restart no longer reads `restarting`. No `NodeKind` is unique to a
restart — `restart_chain` reuses `Signal` / `StopForUpdate` / `Drain` /
`Reconcile` — because "restart" is a property of the DAG's shape, not of
any node. A restart now reads `signal` / `stop_for_update`, then the
agent returns.

`Start` / `Stop` / `PostSwap` run inside a lease-holding ancestor and
re-declare nothing, so they light no pill and the agent reads idle for
those windows. Closing that is the resources-where-constructed work
(#2818), not this change.

Checked with clippy (`--all-targets -D warnings`), `cargo test -p
hive-c0re -p hive-jobq` (321 + 40 passed) and `nix fmt`.

hive-c0re/src/dashboard/state_snapshot.rs

@@ -214,7 +214,8 @@ struct PortConflict {
 #[derive(Serialize)]
 struct TransientView {
     name: String,
-    kind: &'static str,
+    /// Owned: the label is the running node's wire tag, not one of a fixed set.
+    kind: String,
     secs: u64,
 }
 
@@ -533,26 +534,12 @@ fn build_transient_views(
         .filter(|(name, _)| !containers.iter().any(|c| &c.name == *name))
         .map(|(name, st)| TransientView {
             name: name.clone(),
-            kind: transient_label(st.kind),
+            kind: st.label.clone(),
             secs: st.since.elapsed().as_secs(),
         })
         .collect()
 }
 
-fn transient_label(k: crate::coordinator::TransientKind) -> &'static str {
-    use crate::coordinator::TransientKind::{
-        Destroying, Rebuilding, Restarting, Spawning, Starting, Stopping,
-    };
-    match k {
-        Spawning => "spawning",
-        Starting => "starting",
-        Stopping => "stopping",
-        Restarting => "restarting",
-        Rebuilding => "rebuilding",
-        Destroying => "destroying",
-    }
-}
-
 /// Render each pending approval into its dashboard view (short sha for
 /// `MergeConfigPr`, just the name for `Spawn`).
 /// Project a resolved sqlite row into the lean shape the dashboard