harden runtime config and docs

src/lib/fcgi_forward.h

@@ -2,7 +2,7 @@
 
 // Minimal FastCGI client used by the connection brokers (the custom HTTP server
 // dispatcher and the websocket exec child) to render a request through a normal
-// worker on /run/uce.sock instead of rendering wasm in the broker's own forked
+// worker on FCGI_SOCKET_PATH instead of rendering wasm in the broker's own forked
 // process. Wasmtime cannot be safely re-created across fork, so the broker owns
 // the connection but forwards the actual unit invocation to a clean-engine
 // worker — the "broker holds connections, units respond like RENDER()" model.