Slice 3 — OpenAI Realtime brain: swap echo for the brain (#4)

Cargo.toml

@@ -11,6 +11,7 @@ members = [
     "crates/rutster-trunk",
     "crates/rutster-tap",
     "crates/rutster-tap-echo",
+    "crates/rutster-brain-realtime",
     "crates/rutster-spend",
 ]
 
@@ -51,3 +52,10 @@ futures-util = "0.3"
 url = "2"
 # base64 0.22: PCM <-> base64 codec for the v1 wire format (spec §3).
 base64 = "0.22"
+# async-trait 0.1: async fns in trait objects (Tool trait, slice-3 spec §6.1).
+async-trait = "0.1"
+# http 1: Request/Response builders for the OpenAI WS handshake (slice-3
+# spec §5.3). Task 9's main.rs builds the http::Request<...> the tungstenite
+# client sends before WS upgrade; `openai_client::openai_headers` produces
+# the header pairs the caller stuffs into it.
+http = "1"