bxcore: a turn's speaker, SessionUpdated's turn, the session-state messages

Co-Authored-By: ornith-1.5-35b-a3b <agent@wntrmute.dev>

crates/bxcore/tests/fixtures/records/session_speaker.jsonl

@@ -0,0 +1,5 @@
+{"type":"session_start","time":"2026-09-27T09:00:00.000Z","session":"mm-r0000000000000000000000001","epoch":0,"slot":2,"baseline":"000102030405060708090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f"}
+{"type":"user","time":"2026-09-27T09:00:01.000Z","content":"When is the launch?","speaker":"kyle"}
+{"type":"assistant","time":"2026-09-27T09:00:04.000Z","content":"On Thursday.","reasoning_content":null,"tool_calls":[]}
+{"type":"user","time":"2026-09-27T09:01:00.000Z","content":"And the review?"}
+{"type":"assistant","time":"2026-09-27T09:01:03.000Z","content":"On Friday.","reasoning_content":null,"tool_calls":[]}

crates/bxcore/tests/fixtures/wire/session_state.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":true,"msg":{"kind":"session_state","body":{"session":"mm-r0000000000000000000000001"}}}

crates/bxcore/tests/fixtures/wire/session_state_reply.json

@@ -0,0 +1 @@
+{"v":1,"id":1,"final":true,"msg":{"kind":"session_state_reply","body":{"class":"private","untrusted":true}}}

crates/bxcore/tests/fixtures/wire/session_updated.json

@@ -1 +1 @@
-{"v":1,"id":1,"final":true,"msg":{"kind":"session_updated","body":{"session":"mm-r0000000000000000000000001"}}}
+{"v":1,"id":1,"final":true,"msg":{"kind":"session_updated","body":{"session":"mm-r0000000000000000000000001","turn":3}}}

crates/bxcore/tests/fixtures/wire/turn_speaker.json

@@ -0,0 +1 @@
+{"v":1,"id":3,"final":true,"msg":{"kind":"turn","body":{"session":"mm-r0000000000000000000000001","content":"What time is it?","resume":true,"speaker":"kyle"}}}