show the model that answered instead of the bare harness string

the picker rendered the literal `claude-code` for any chat that named no
tier. that is DEFAULT_MODEL — the bare harness — and it routes correctly
(no --model is passed, so the cli picks for itself) but names no catalogue
entry, so radix matched no item and the fallback from 773f0e1c printed the
raw string's last segment.

officer cannot answer this because it deliberately did not choose. the
harness does, in its system.init `model` field, which the parser was
discarding. so: emit it as a `model:resolved` chat event, translate it to an
officer id in turn-stream, and forward it to the client only when the turn
named no tier.

that last condition is the load-bearing one. the alias map is lossy in one
direction — opus[1m] and opusplan both answer as claude-opus-5 — so
forwarding unconditionally would silently relabel a user's own choice as
plain opus.

display only, and three ways: not durable (like session:claude), never
recorded to chat_session_models, and never written into the client's
selectedModel or the reattach ref. storing it would pin a session to
whatever the cli defaulted to on its first turn, which is the freedom the
bare harness exists to preserve.

untested against a live turn — the parser and translator have unit tests,
the websocket gate does not.

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

src/servers/sidecar/claude/turn-stream.test.ts

@@ -17,6 +17,34 @@ function run(events: ChatEvent[]) {
   };
 }
 
+describe('the model the harness resolved for itself', () => {
+  test('travels as an Officer id and is never persisted', () => {
+    const { all, durable, types } = run([{ type: 'model:resolved', apiModel: 'claude-opus-5' }]);
+    expect(types).toEqual(['model:resolved']);
+    expect(all[0]!.msg).toEqual({ type: 'model:resolved', model: 'claude-code/opus' });
+    // Live-only for the same reason as `session:claude`: it marks no boundary, and a replay learns the
+    // model from the session row instead.
+    expect(durable).toHaveLength(0);
+  });
+
+  test('an id with no honest Officer equivalent is dropped rather than forwarded raw', () => {
+    // mythos has no catalogue entry on this machine, and `<synthetic>` is not a model at all. Offering
+    // either to the picker is worse than leaving it as it was.
+    expect(run([{ type: 'model:resolved', apiModel: 'claude-mythos-5' }]).all).toHaveLength(0);
+    expect(run([{ type: 'model:resolved', apiModel: '<synthetic>' }]).all).toHaveLength(0);
+  });
+
+  test('does not flush an open delta buffer', () => {
+    // It says nothing about WHERE in the conversation anything happened, so cutting the sentence the
+    // agent is mid-way through would be a boundary the event does not describe.
+    const { types } = run([
+      { type: 'delta', text: 'thinking' },
+      { type: 'model:resolved', apiModel: 'claude-sonnet-5' },
+    ]);
+    expect(types).toEqual(['assistant:delta', 'model:resolved']);
+  });
+});
+
 describe('createTurnStream', () => {
   test('deltas are live-only and never durable', () => {
     const { all, durable } = run([