Add cohere client (#236)

* Add CohereModel

* Format

* Update pyproject.toml

* Update src/strands/models/cohere.py

* Revert cusom cli, keep only compat layer

* Format and fixes

Author: billytrend-cohere

tests-integ/test_model_cohere.py

@@ -0,0 +1,47 @@
+import os
+
+import pytest
+
+import strands
+from strands import Agent
+from strands.models.openai import OpenAIModel
+
+
+@pytest.fixture
+def model():
+    return OpenAIModel(
+        client_args={
+            "base_url": "https://api.cohere.com/compatibility/v1",
+            "api_key": os.getenv("CO_API_KEY"),
+        },
+        model_id="command-a-03-2025",
+        params={"stream_options": None},
+    )
+
+
+@pytest.fixture
+def tools():
+    @strands.tool
+    def tool_time() -> str:
+        return "12:00"
+
+    @strands.tool
+    def tool_weather() -> str:
+        return "sunny"
+
+    return [tool_time, tool_weather]
+
+
+@pytest.fixture
+def agent(model, tools):
+    return Agent(model=model, tools=tools)
+
+
+@pytest.mark.skipif(
+    "CO_API_KEY" not in os.environ,
+    reason="CO_API_KEY environment variable missing",
+)
+def test_agent(agent):
+    result = agent("What is the time and weather in New York?")
+    text = result.message["content"][0]["text"].lower()
+    assert all(string in text for string in ["12:00", "sunny"])