Update to Python 1.28.0. Add codeowners rules for nexus samples

.github/CODEOWNERS

@@ -1 +1,8 @@
 * @temporalio/sdk
+
+# The Nexus team owns any folder whose name starts or ends with "nexus",
+# both at the repo root and under tests/
+/nexus*/ @temporalio/nexus
+/*nexus/ @temporalio/nexus
+/tests/nexus*/ @temporalio/nexus
+/tests/*nexus/ @temporalio/nexus

pyproject.toml

@@ -6,7 +6,7 @@ authors = [{ name = "Temporal Technologies Inc", email = "sdk@temporal.io" }]
 requires-python = ">=3.10"
 readme = "README.md"
 license = "MIT"
-dependencies = ["temporalio>=1.27.2,<2", "protobuf>=5.29.6,<6"]
+dependencies = ["temporalio>=1.28.0,<2", "protobuf>=5.29.6,<6"]
 
 [project.urls]
 Homepage = "https://github.com/temporalio/samples-python"
@@ -41,13 +41,13 @@ gevent = ["gevent>=25.4.2 ; python_version >= '3.8'"]
 langsmith-tracing = [
     "openai>=1.4.0",
     "langsmith>=0.7.0",
-    "temporalio[pydantic,langsmith]>=1.27.0",
+    "temporalio[pydantic,langsmith]>=1.28.0",
 ]
 langgraph = [
     "langgraph>=1.1.3",
     "langchain>=0.3.0",
     "langchain-anthropic>=0.3.0",
-    "temporalio[langgraph,langsmith]>=1.27.0",
+    "temporalio[langgraph,langsmith]>=1.28.0",
 ]
 nexus = ["nexus-rpc>=1.1.0,<2"]
 open-telemetry = [
@@ -56,7 +56,7 @@ open-telemetry = [
 ]
 openai-agents = [
     "openai-agents[litellm] >= 0.14.1",
-    "temporalio[openai-agents,opentelemetry] >= 1.27.0",
+    "temporalio[openai-agents,opentelemetry] >= 1.28.0",
     "requests>=2.32.0,<3",
 ]
 pydantic-converter = ["pydantic>=2.10.6,<3"]
@@ -71,9 +71,6 @@ cloud-export-to-parquet = [
 
 [tool.uv]
 constraint-dependencies = [
-    # langsmith 0.7.34 changed its aio_to_thread signature; temporalio.contrib.langsmith
-    # 1.27.2 still patches the older signature, causing workflow task retries to hang CI.
-    "langsmith<0.7.34",
     # yarl 1.24.0 was published without an sdist and only has cp310 wheels, so it cannot
     # install on the Python 3.14 CI jobs.
     "yarl!=1.24.0",