fix(state): include finish_reason in conversation replay

SELECT in get_messages_as_conversation() was missing finish_reason, so
assistant messages round-tripped through replay (including /branch copies)
silently dropped the provider's stop signal. Adds it to the SELECT, restores
it on assistant rows, and locks it in with a round-trip test.

hermes_state.py

@@ -1464,8 +1464,8 @@ class SessionDB:
             placeholders = ",".join("?" for _ in session_ids)
             rows = self._conn.execute(
                 "SELECT role, content, tool_call_id, tool_calls, tool_name, "
-                "reasoning, reasoning_content, reasoning_details, codex_reasoning_items, "
-                "codex_message_items "
+                "finish_reason, reasoning, reasoning_content, reasoning_details, "
+                "codex_reasoning_items, codex_message_items "
                 f"FROM messages WHERE session_id IN ({placeholders}) ORDER BY timestamp, id",
                 tuple(session_ids),
             ).fetchall()
@@ -1490,6 +1490,8 @@ class SessionDB:
             # that replay reasoning (OpenRouter, OpenAI, Nous) receive
             # coherent multi-turn reasoning context.
             if row["role"] == "assistant":
+                if row["finish_reason"]:
+                    msg["finish_reason"] = row["finish_reason"]
                 if row["reasoning"]:
                     msg["reasoning"] = row["reasoning"]
                 if row["reasoning_content"] is not None: