[Test] Anthropic Passthrough: Bump Thinking Tests Off Legacy Sonnet 4 Alias

base_anthropic_messages_test.test_anthropic_messages_with_thinking and
test_anthropic_streaming_with_thinking still pinned to
claude-4-sonnet-20250514 — the same legacy alias Anthropic no longer
recognizes under freshly issued keys. The other four tests in this base
class already use claude-sonnet-4-5-20250929; these two were missed.

Bump to claude-haiku-4-5-20251001 (supports_reasoning=true, no upcoming
deprecation). Subclasses including TestAnthropicPassthroughBasic
inherit these methods.

tests/pass_through_tests/base_anthropic_messages_test.py

@@ -54,7 +54,7 @@ class BaseAnthropicMessagesTest(ABC):
         print("making request to anthropic passthrough with thinking")
         client = self.get_client()
         response = client.messages.create(
-            model="claude-4-sonnet-20250514",
+            model="claude-haiku-4-5-20251001",
             max_tokens=20000,
             thinking={"type": "enabled", "budget_tokens": 16000},
             messages=[
@@ -75,7 +75,7 @@ class BaseAnthropicMessagesTest(ABC):
         collected_response = []
         client = self.get_client()
         with client.messages.stream(
-            model="claude-4-sonnet-20250514",
+            model="claude-haiku-4-5-20251001",
             max_tokens=20000,
             thinking={"type": "enabled", "budget_tokens": 16000},
             messages=[