move opencode's turn output into its own sidecar

The second copy of the same problem. The opencode sidecar reported raw
ChatEvents and officer translated them, buffered the assistant text and wrote
every durable message to chat_session_events — so an officer restart mid-turn
lost whatever the model had produced since the last write, and `connect.ts`
dropped the events that arrived while it was down without a word.

Both harnesses speak ChatEvents, so the sidecar reuses the agent's session log
verbatim: translate, commit, then deliver the finished message with its cursor
id as `opencode:message`. Officer folds it into the in-memory transcript and
relays it, exactly as it now does for claude — `createEventHandler` (166 lines,
a duplicate of turn-stream.ts) and `emitToSession` are gone, and nothing in
officer writes to chat_session_events any more.

`opencode:event` stops being a wire event; it is the runner's internal report to
the sidecar it runs in, typed as such so it cannot leak back onto the socket.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/servers/sidecar/protocol.ts

@@ -1,4 +1,4 @@
-import type { MessageCost, ChatEvent, TurnMessage } from '../api/chat/types';
+import type { MessageCost, TurnMessage } from '../api/chat/types';
 
 // ── Envelope ──
 
@@ -54,9 +54,12 @@ export type SidecarEvent =
   | { type: 'email:new'; userEmail: string }
   // OpenCode — the sidecar reports where its `opencode serve` is listening (random port) on connect
   | { type: 'opencode:server'; port: number }
-  // OpenCode turn streaming (analog of claude:*): spawned ack, per-event stream, session id report
+  // OpenCode turn streaming (analog of claude:*): spawned ack, per-message stream, session id report
   | { type: 'opencode:spawned'; id: string; sessionKey: string }
-  | { type: 'opencode:event'; sessionKey: string; event: ChatEvent }
+  // Same contract as `claude:message`: a finished turn message the sidecar has already committed to
+  // chat_session_events, plus the cursor id it landed on. Officer relays it and folds it into its
+  // in-memory transcript; it does not translate or persist.
+  | { type: 'opencode:message'; sessionKey: string; msg: TurnMessage; seq?: number }
   | { type: 'opencode:session'; sessionKey: string; sessionId: string }
   | { type: 'opencode:error'; id: string; error: string }
   // Music — the sidecar reports where its audio-streaming HTTP server is listening (random port) on connect
@@ -117,6 +120,7 @@ export type OpenCodeRunParams = {
   cwd?: string; // passed to `opencode run --dir` — hard-re-anchors tools to this directory
   model?: string; // `providerID/modelID` (e.g. opencode/claude-haiku-4-5); passed to --model verbatim
   resumeSessionId?: string; // OpenCode `ses_…` id to continue (`--session`)
+  durable?: boolean; // commit turn output to chat_session_events (default true) — see ClaudeSpawnStreamingParams
 };
 
 // ── VNC types ──