Enforce HYPERDX_OTLP_ENDPOINT path at runtime

The documented requirement (env var MUST include ``/v1/traces``) was
only enforced through docs, not the test itself. Because the OTel
SDK swallows exporter-side errors and ``force_flush`` returns True
regardless of the HTTP response, a host-only URL would POST to ``/``,
HyperDX would 404, and the test would still report green. This is the
silent-failure mode the test's docstring already warned about and
the one we hit on this PR's manual validation.

Assert the endpoint ends with ``/v1/traces`` before constructing the
exporter; the assert raises with a pointer to the expected shape if
the env var is misconfigured.

Author: chris-colinsky

tests/integration/test_otel_hyperdx_export.py

@@ -60,12 +60,24 @@ async def test_otel_observer_pipeline_drains_with_hyperdx_exporter() -> None:
     from openarmature.graph import END, GraphBuilder, State
     from openarmature.observability.otel import OTelObserver
 
+    # Enforce the documented endpoint shape at runtime. The
+    # ``OTLPSpanExporter`` uses the URL verbatim and does not append
+    # ``/v1/traces`` itself, so a host-only URL POSTs to ``/`` and
+    # HyperDX 404s; the SDK swallows that response and ``force_flush``
+    # still returns True, which would mask a misconfigured env var
+    # behind a passing test.
+    endpoint = os.environ["HYPERDX_OTLP_ENDPOINT"]
+    assert endpoint.endswith("/v1/traces"), (
+        f"HYPERDX_OTLP_ENDPOINT must end with /v1/traces (got {endpoint!r}); "
+        "OTLPSpanExporter uses the URL verbatim and does not append paths."
+    )
+
     # HyperDX accepts the API key as a bare ``authorization`` header
     # value (no ``Bearer`` prefix). Other OTLP collectors that expect
     # ``Bearer <token>`` will need the caller to format the header
     # themselves; this is the documented HyperDX shape.
     exporter = OTLPSpanExporter(
-        endpoint=os.environ["HYPERDX_OTLP_ENDPOINT"],
+        endpoint=endpoint,
         headers={"authorization": os.environ["HYPERDX_API_KEY"]},
     )