phase D: delete the subprocess path

The serve is now the only way an opencode turn runs. runner.ts and its tests are gone, and
so is the OPENCODE_TURNS switch — there is no fallback engine any more, and the recovery for
a bad day is git rather than a config flag. Deliberate, and cheap right now precisely because
nothing depends on opencode yet.

What goes with it: mapRunLine and its NDJSON fixtures, the temp-file spill for --file image
attachments, the supersede-and-kill dance, the process watchdogs, the pidfile-adjacent child
tracking, and stopAllOpenCodeTurns. All of it existed to work around stdin being /dev/null.

Verified after deletion, with no env var set at all: tool call, tool result, 5 streaming
deltas, text and cost, through the real chat socket.

Also corrected the comments the deletion falsified rather than leaving them to mislead — the
module header, the wire contract description of opencode:run-streaming, and serve-runner own
header, which still announced itself as off by default.

One difference worth stating: shutdown no longer kills anything. Turns run inside the serve,
which is a separate process that survives us, so officer stops routing them and says so in
the transcript. When a subprocess ran the turn, failing to kill it orphaned it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/servers/sidecar/protocol.ts

@@ -26,8 +26,8 @@ export type LiveClaudeSession = {
 };
 
 /**
- * An OpenCode turn in flight. Only ever the generating ones — see `listRunningOpenCodeTurns` for why
- * this carries neither `isGenerating` (it is always true) nor `pendingTasks` (no such concept).
+ * An OpenCode turn in flight. Only ever the generating ones, which is why it carries neither
+ * `isGenerating` (always true) nor `pendingTasks` (no such concept on this harness).
  *
  * It deliberately carries no id for OpenCode's own `ses_…` session, and does not need to: the sidecar
  * only ever knows its own `sessionKey`, while the `ses_…` is reported separately over `opencode:session`
@@ -63,12 +63,13 @@ export type SidecarCommand =
   // records are in memory and die with `pm2 restart officer`, while the agent keeps running. Without it
   // a live session is invisible until a browser happens to reconnect to it by id.
   | { type: 'claude:list'; id: string }
-  // OpenCode — drive a turn via `opencode run … --format json` (tools re-anchored to cwd via --dir)
+  // OpenCode — drive a turn through the serve (POST /api/session/{id}/prompt), anchored to the chat cwd
+  // by a per-request location header. Was an `opencode run` subprocess until 2026-08-10.
   | { type: 'opencode:run-streaming'; id: string; params: OpenCodeRunParams }
   | { type: 'opencode:kill'; id: string; sessionKey: string }
   // Which OpenCode turns are running right now. The counterpart of `claude:list`, and thinner for a
   // reason: OpenCode has no warm session between turns, so there is nothing to report but the running
-  // ones. See `listRunningOpenCodeTurns`.
+  // ones — see `listRunningServeTurns`.
   | { type: 'opencode:list'; id: string }
   // VNC
   | { type: 'vnc:start'; id: string; params: VncStartParams }