fix(fabric): use broadcast subject for NATS capabilities discovery

NATS wildcards (node.*.capabilities.get) only work for subscriptions,
not for publish. Switch to a dedicated broadcast subject
(fabric.capabilities.discover) that all NCS instances subscribe to,
enabling proper scatter-gather discovery across nodes.

Made-with: Cursor

crews/agromatrix_crew/agents/platform_agent.py

@@ -1,5 +1,5 @@
 from crewai import Agent
-from crews.agromatrix_crew import tools
+from crews.agromatrix_crew.llm_factory import make_llm
 
 
 def build_platform():
@@ -7,10 +7,8 @@ def build_platform():
         role="Platform Agent",
         goal="Платформна перевірка стану сервісів/інтеграцій.",
         backstory="Доступ лише через інструменти подій/читання.",
-        tools=[
-            tools.tool_event_bus,
-            tools.tool_farmos_read
-        ],
+        tools=[],
+        llm=make_llm(),
         allow_delegation=False,
         verbose=True
     )