fix(kimi): omit temperature entirely for Kimi/Moonshot models (#13157)

Kimi's gateway selects the correct temperature server-side based on the
active mode (thinking -> 1.0, non-thinking -> 0.6).  Sending any
temperature value — even the previously "correct" one — conflicts with
gateway-managed defaults.

Replaces the old approach of forcing specific temperature values (0.6
for non-thinking, 1.0 for thinking) with an OMIT_TEMPERATURE sentinel
that tells all call sites to strip the temperature key from API kwargs
entirely.

Changes:
- agent/auxiliary_client.py: OMIT_TEMPERATURE sentinel, _is_kimi_model()
  prefix check (covers all kimi-* models), _fixed_temperature_for_model()
  returns sentinel for kimi models.  _build_call_kwargs() strips temp.
- run_agent.py: _build_api_kwargs, flush_memories, and summary generation
  paths all handle the sentinel by popping/omitting temperature.
- trajectory_compressor.py: _effective_temperature_for_model returns None
  for kimi (sentinel mapped), direct client calls use kwargs dict to
  conditionally include temperature.
- mini_swe_runner.py: same sentinel handling via wrapper function.
- 6 test files updated: all 'forces temperature X' assertions replaced
  with 'temperature not in kwargs' assertions.

Net: -76 lines (171 added, 247 removed).
Inspired by PR #13137 (@kshitijk4poor).

tests/run_agent/test_provider_parity.py

@@ -251,8 +251,12 @@ class TestBuildApiKwargsChatCompletionsServiceTier:
         assert "service_tier" not in kwargs
 
 
-class TestBuildApiKwargsKimiFixedTemperature:
-    def test_kimi_for_coding_forces_temperature_on_main_chat_path(self, monkeypatch):
+class TestBuildApiKwargsKimiNoTemperatureOverride:
+    def test_kimi_for_coding_omits_temperature(self, monkeypatch):
+        """Temperature should NOT be set client-side for Kimi models.
+
+        The Kimi gateway selects the correct temperature server-side.
+        """
         agent = _make_agent(
             monkeypatch,
             "kimi-coding",
@@ -261,7 +265,7 @@ class TestBuildApiKwargsKimiFixedTemperature:
         )
         messages = [{"role": "user", "content": "hi"}]
         kwargs = agent._build_api_kwargs(messages)
-        assert kwargs["temperature"] == 0.6
+        assert "temperature" not in kwargs
 
 
 class TestBuildApiKwargsAIGateway: