fix(deps): add arize-phoenix server to [otel] extra so 'phoenix serve' works

Customer-facing docs (README.md, AGENTS.md, docs/quickstart.md) instruct
users to run 'uv run phoenix serve' to view traces locally, but the
[otel] extra only had arize-phoenix-otel (the SDK client) and not
arize-phoenix (the server). Customers following the quickstart hit
'phoenix: program not found'.

Loosens opentelemetry-{api,sdk} pin from >=1.41 to >=1.39 to overlap
with arize-phoenix's transitive constraint (via pydantic-ai/logfire).
Our OTel usage is API-stable and works on both ranges.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: changliu2

pyproject.toml

@@ -17,10 +17,11 @@ dependencies = [
 
 [project.optional-dependencies]
 otel = [
+  "arize-phoenix>=15.0.0",
   "arize-phoenix-otel>=0.15.0",
   "openinference-instrumentation-langchain>=0.1.62",
-  "opentelemetry-api>=1.41.0",
-  "opentelemetry-sdk>=1.41.0",
+  "opentelemetry-api>=1.39.0",
+  "opentelemetry-sdk>=1.39.0",
 ]
 langgraph = [
   "langchain-core>=1.3.0",