feat(dashboard): node-aware queue render + buildSlots option

each queue card now shows its DAG's node chain (per-node state, step,
build-log link), fixing 'queue jumps don't show on the dashboard'.
live-log panel keys off the running node's log. new
services.hyperhive.c0re.buildSlots option (default 1) threads the
concurrent nix-build count into serve.json.

nix/modules/hive-c0re.nix

@@ -52,6 +52,7 @@ let
     agent_cpu_quota = cfg.agentCpuQuota;
     agent_memory_max = cfg.agentMemoryMax;
     model_prices = cfg.modelPrices;
+    build_slots = cfg.buildSlots;
   };
 
   # Stylix theme integration (zero-op auto-detect). When the operator's
@@ -771,6 +772,22 @@ in
         `"2G"`.
       '';
     };
+
+    buildSlots = lib.mkOption {
+      type = lib.types.ints.positive;
+      default = 1;
+      example = 2;
+      description = ''
+        Number of nix-heavy job-queue nodes (container prebuilds,
+        profile swaps, first-spawn creates, meta lock bumps) hive-c0re
+        runs concurrently. The default of 1 serializes all heavy nix
+        work like the pre-DAG rebuild queue did; raise it on hosts with
+        the cores/RAM to build several agent toplevels at once.
+        Per-agent correctness is independent of this count — each
+        agent's container-affecting operations are serialized by its
+        lifecycle lease regardless.
+      '';
+    };
   };
 
   config = lib.mkIf cfg.enable {