feat: implement skeleton phase

src/beaver_gateway/cli.py

@@ -0,0 +1,28 @@
+"""Process entrypoint.
+
+Phase 0.3 — load the user's ``/config/config.py`` via
+``config_loader``, build registries, print the
+``loaded N agents, M mcps, K frontends`` line from the Phase 0 DoD,
+exit cleanly. Phase 0.4 will install uvloop and start uvicorn(s) for
+the frontends and the internal MCP app.
+"""
+
+from __future__ import annotations
+
+from beaver_gateway import config_loader
+from beaver_gateway.core.registry import AgentRegistry, McpRegistry
+from beaver_gateway.settings import Settings
+
+
+def main() -> None:
+    settings = Settings()  # ty: ignore[missing-argument]
+
+    gateway = config_loader.load(settings.config_path)
+
+    agents = AgentRegistry(gateway.agents)
+    mcps = McpRegistry(gateway.mcps)
+
+    print(
+        f"beaver-gateway: loaded {len(agents)} agents, "
+        f"{len(mcps)} mcps, {len(gateway.frontends)} frontends"
+    )