Add multi-turn Assistent session diagnostics to the Debug API.

POST /assistent/session + /chat with rich per-turn traces (patch, Exact merge, compact_context); chat-eval wraps one session turn. Docs playbook and unit/HTTP tests included.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/test_debug_api.py

@@ -193,24 +193,41 @@ def test_extract_assistent_patch():
 
 def test_chat_eval_mocked_http(monkeypatch, tmp_path):
     from gpu_rent import debug_assistent
+    from gpu_rent import debug_assistent_session as das
 
     _auth_env(monkeypatch, tmp_path)
     cfg = load_config(require_auth=True)
+    das.reset_session_store_for_tests()
 
     monkeypatch.setattr(
-        debug_assistent,
+        das,
         "_swarm_base",
         lambda cfg: ("http://127.0.0.1:17801", "local"),
     )
     monkeypatch.setattr(
-        debug_assistent,
+        das,
         "_session_id",
         lambda base: ("sess-1", None, 5.0),
     )
+    monkeypatch.setattr(
+        das,
+        "_resolve_chat_model",
+        lambda cfg, base, sid, model=None: ("qwen3-vl:8b", "qwen3-vl:8b"),
+    )
 
     calls: list[tuple[str, dict]] = []
 
     def fake_http(url, *, method="GET", body=None, timeout=12.0):
+        if url.endswith("/API/AssistentGetConfig"):
+            return True, {
+                "success": True,
+                "persona": "leonid",
+                "exact": {
+                    "profiles": {"turbo": {"steps": 8, "cfg": 1, "sigma_shift": 1.15}}
+                },
+                "skills": [],
+                "enabled_skills": [],
+            }, 8.0
         if url.endswith("/API/AssistentListModels"):
             return True, {"preferred": "qwen3-vl:8b", "models": ["qwen3-vl:8b"]}, 10.0
         if url.endswith("/API/AssistentChat"):
@@ -223,7 +240,7 @@ def test_chat_eval_mocked_http(monkeypatch, tmp_path):
             return True, {"success": True, "reply": reply, "model": "qwen3-vl:8b"}, 42.0
         return False, "unexpected " + url, 1.0
 
-    monkeypatch.setattr(debug_assistent, "_http_json", fake_http)
+    monkeypatch.setattr(das, "_http_json", fake_http)
 
     out = debug_assistent.run_assistent_chat_eval(
         cfg,
@@ -240,6 +257,7 @@ def test_chat_eval_mocked_http(monkeypatch, tmp_path):
     assert out["patch"]["cfg"] == 1
     assert out["patch"]["aspect"] == "3:4"
     assert "turbo" in (out["reply_prose"] or "").lower() or "turbo" in (out["reply"] or "").lower()
+    assert out.get("trace") and out["trace"].get("exact_merge")
     assert calls and calls[0][1]["session_id"] == "sess-1"
     assert calls[0][1]["messages"][0]["content"] == "какой checkpoint?"
     assert calls[0][1]["includeBase"] is True