feat(llm): add Amazon Bedrock as a first-class provider

Bedrock uses the Converse API (langchain-aws) and the AWS credential chain, so
it has its own client like Anthropic/Google rather than the OpenAI-compatible
registry. langchain-aws is an optional dependency (pip install ".[bedrock]"),
lazy-imported with a clear install hint; importing the package never requires
it. The model name is a Bedrock model ID / inference profile ID.

tests/test_bedrock_provider.py

@@ -0,0 +1,46 @@
+"""Amazon Bedrock — first-class native client via the optional langchain-aws extra.
+
+Auth uses the AWS credential chain (no single key env); the model is a Bedrock
+model ID / inference profile ID; langchain-aws is imported lazily with a clear
+install hint when the [bedrock] extra is absent.
+"""
+import sys
+
+import pytest
+
+from tradingagents.llm_clients.api_key_env import get_api_key_env
+from tradingagents.llm_clients.factory import create_llm_client
+from tradingagents.llm_clients.validators import validate_model
+
+
+@pytest.mark.unit
+def test_factory_routes_bedrock():
+    client = create_llm_client("bedrock", "us.anthropic.claude-opus-4-8-v1:0")
+    assert type(client).__name__ == "BedrockClient"
+
+
+@pytest.mark.unit
+def test_bedrock_any_model_and_no_key_env():
+    assert validate_model("bedrock", "any.model-id:0") is True
+    # Bedrock uses the AWS credential chain, so there is no single key env.
+    assert get_api_key_env("bedrock") is None
+
+
+@pytest.mark.unit
+def test_helpful_error_when_langchain_aws_absent(monkeypatch):
+    import tradingagents.llm_clients.bedrock_client as bc
+    monkeypatch.setattr(bc, "_BEDROCK_CLASS", None)
+    monkeypatch.setitem(sys.modules, "langchain_aws", None)  # force ImportError on import
+    with pytest.raises(ImportError, match=r"bedrock"):
+        create_llm_client("bedrock", "m").get_llm()
+
+
+@pytest.mark.unit
+def test_construction_when_extra_installed(monkeypatch):
+    pytest.importorskip("langchain_aws")
+    import tradingagents.llm_clients.bedrock_client as bc
+    monkeypatch.setattr(bc, "_BEDROCK_CLASS", None)
+    monkeypatch.setenv("AWS_DEFAULT_REGION", "eu-west-1")
+    llm = create_llm_client("bedrock", "us.anthropic.claude-sonnet-4-6-v1:0").get_llm()
+    assert type(llm).__name__ == "NormalizedChatBedrockConverse"
+    assert llm.region_name == "eu-west-1"