refactor(#2441): update queue consumers + docs for agent-per-node

DagView no longer has a DAG-level agent, so consumers derive it from the
per-node agents:
- hivectl dag_progress.rs: dag_agents(d) helper (distinct node agents,
  comma-joined) in place of d.agent.
- dashboard builds.js: entryAgents(entry) helper likewise for the
  rebuild-queue card + live-log header + cancel confirms.
- docs/coordinator.md: lease prose (node-agent-keyed, global per agent),
  wire shape (NodeView.agent, no DagView.agent), and dropped the removed
  dedup section.

docs/coordinator.md

@@ -22,7 +22,7 @@ The **DAG** is the unit of dedup / cancel / approval-resolution and the
 dashboard group; the **node** is the unit of scheduling / execution /
 build-log / step label. Deps are intra-DAG edges only (`AfterOk` by default:
 the dep must succeed, a failed/cancelled dep cancels the dependent —
-cancel-downstream). Cross-DAG ordering comes from the per-agent lease + dedup,
+cancel-downstream). Cross-DAG ordering comes from the per-agent lease,
 never from edges between DAGs. Submit-time validation (petgraph `toposort`)
 rejects cyclic specs outright, fixing the old queue's "circular dep silently
 deadlocks" caveat.
@@ -139,11 +139,13 @@ resources are free. Resources:
 
 1. **Build slots** — `services.hyperhive.c0re.buildSlots` permits (default 1),
    held by nix-heavy nodes for the node's duration.
-2. **Per-agent lifecycle lease** — DAG-scoped: acquired at the DAG's first
-   container-affecting node (`StopForUpdate`, `Swap`, `Signal`, `Drain`,
-   `Reconcile`, `WriteDropin`, `Create`, `ApprovalDeploy`), held until the DAG
-   is terminal, so two lifecycle DAGs for one agent never interleave their
-   container ops. **Lease-exempt**: `Prebuild`, `MetaLock`, `WritePermFile` —
+2. **Per-agent lifecycle lease** — keyed on the **node's** agent (agent is
+   per-node; a DAG can span agents) and globally exclusive per agent across
+   all DAGs: acquired at a container-affecting node (`StopForUpdate`, `Swap`,
+   `Signal`, `Drain`, `Reconcile`, `WriteDropin`, `Create`, `ApprovalDeploy`),
+   held by the owning DAG until it's terminal, so two DAGs never interleave
+   container ops on the same agent. A DAG touching several agents holds one
+   lease per agent. **Lease-exempt**: `Prebuild`, `MetaLock`, `WritePermFile` —
    they touch the store / meta, not the running container, which is exactly
    why a stop can land while another DAG's prebuild is still building.
 
@@ -156,14 +158,11 @@ The queue is in-memory only and lost on hive-c0re restart — deliberate:
 desired state is re-derived at boot from the DB + rev markers (see _Boot
 reconcile_), so there is no durable-recovery machinery to go wrong.
 
-### Dedup, cancel, history
+### Cancel, history
 
-Dedup at **DAG granularity**: a repeat submit against a DAG whose roll-up is
-still `Queued` with the same `(template, agent, parent_id, approval_id)` —
-plus `inputs` for meta-updates and the perm-type discriminant for perm
-changes — returns the existing id and appends an "also requested by …" line.
-`parent_id` in the key keeps a cascade child from collapsing into a
-standalone or sweep rebuild. Running/terminal DAGs never dedup.
+Submit-time dedup was removed with the agent-per-node move (a multi-agent DAG
+has no single agent to key a dedup on), so every submit enqueues a fresh DAG;
+whether any dedup needs reintroducing is tracked as a follow-up.
 
 Cancel only applies to still-fully-queued DAGs (an in-flight nix build isn't
 interruptible); `cancel_children` cancels a parent's still-queued child DAGs.
@@ -186,12 +185,14 @@ of dangling it).
 ### Wire shape
 
 `RebuildQueueChanged { seq, queue: [DagView…] }` (event name kept). Each
-`DagView` carries the old entry-level fields (`id`, `kind` = template string,
-roll-up `state`, `agent`, `source`, `parent_id`, `reason`, timestamps,
-`inputs`, `approval_id`) plus `nodes: [NodeView…]` — per-node `kind`, `deps`,
-`state`, `step`, `build_log_id`, timestamps, `error`. Step labels and build
-logs are **per-node**; the dashboard renders the node chain on each queue
-card and keys the live-log panel off the running node.
+`DagView` carries the entry-level fields (`id`, `kind` = template string,
+roll-up `state`, `source`, `parent_id`, `reason`, timestamps, `inputs`,
+`approval_id`) plus `nodes: [NodeView…]` — per-node `agent`, `kind`, `deps`,
+`state`, `step`, `build_log_id`, timestamps, `error`. There is **no
+DAG-level `agent`** (agent is per-node, so a DAG can span agents); consumers
+derive a DAG's agent(s) from its nodes. Step labels and build logs are
+**per-node**; the dashboard renders the node chain on each queue card and
+keys the live-log panel off the running node.
 
 ---