test(lfx): install the otel extra in the dev group

The lfx test job runs `uv sync --dev` in src/lfx, which resolves the lfx
member alone and so uninstalls the opentelemetry packages the full langflow
install happens to provide. test_serve_app_flow_span's subprocess probe then
failed with ModuleNotFoundError, and it passed locally only because langflow
was in the venv.

Depend on the extra itself rather than copying its six pins, so the two
cannot drift.

Author: ogabrielluiz

src/lfx/pyproject.toml

@@ -140,6 +140,10 @@ dev = [
     "coverage>=7.9.2",
     "hypothesis>=6.136.3",
     "langchain-anthropic~=1.4.6",
+    # The otel extra itself, so the observability tests exercise the real exporters. Bare lfx
+    # still ships without them: the tests that assert the no-otel path force the condition by
+    # blocking the import rather than by relying on the extra being absent here.
+    "lfx[otel]",
     "pytest>=9.0.3",
     "pytest-asyncio>=0.26.0",
     "pytest-cov>=7.0.0",