fix(ci): stop a filterwarnings class path aborting the 3.9/3.10 test session

`[tool.pytest.ini_options] filterwarnings` carried
`ignore::starlette.exceptions.StarletteDeprecationWarning`. pytest resolves
that class while parsing config, so on the 3.9/3.10 matrix legs - where the
resolvable starlette predates the class - it raised

    AttributeError: module 'starlette.exceptions' has no attribute
    'StarletteDeprecationWarning'

and aborted the whole session with a usage error (exit 4) before collecting a
single test.

Register the filter from conftest instead, where a missing class degrades to a
no-op. It goes through `addinivalue_line` rather than a module-level
`warnings.filterwarnings` call because pytest runs each test inside its own
`catch_warnings()` seeded from the ini filters, which discards anything
registered at conftest import time. The warning subclasses UserWarning, not
DeprecationWarning, so there is no stdlib category to substitute.

Suppression behaviour is unchanged on 3.11+; verified the warnings summary is
empty again.

Author: qectorlab

pyproject.toml

@@ -172,9 +172,11 @@ python_files = ["test_*.py"]
 python_classes = ["Test*"]
 python_functions = ["test_*"]
 filterwarnings = [
-    # Starlette's TestClient warns that httpx is deprecated in favor of httpx2;
-    # this is upstream noise, not actionable from this project.
-    "ignore::starlette.exceptions.StarletteDeprecationWarning",
+    # Starlette's TestClient deprecation warning is registered in
+    # python/tests/conftest.py, NOT here. pytest resolves a class path in this
+    # list at config-parse time, so naming a class that a older starlette does
+    # not have aborts the entire session with a usage error (exit 4) on the
+    # 3.9/3.10 legs. conftest can tolerate its absence; this list cannot.
 ]
 
 [tool.mypy]

python/tests/conftest.py

@@ -85,6 +85,29 @@ def _demote_repo_source_dir() -> None:
     os.environ.setdefault("QECTOR_TESTS_USE_INSTALLED", "1")
 
 
+# Starlette's TestClient emits a deprecation warning that is upstream noise, not
+# actionable here. This lived in `[tool.pytest.ini_options] filterwarnings` as
+# `ignore::starlette.exceptions.StarletteDeprecationWarning`, but pytest resolves
+# that class at config-parse time: on the 3.9/3.10 matrix legs the resolvable
+# starlette is older, has no such attribute, and pytest aborts the whole session
+# with a usage error (exit 4) before collecting a single test. Registering it
+# here instead degrades to a no-op when the class is absent.
+#
+# Note it subclasses UserWarning, not DeprecationWarning, so there is no stdlib
+# category to filter on as a substitute.
+#
+# It has to go through `addinivalue_line` rather than a module-level
+# `warnings.filterwarnings` call: pytest runs each test inside its own
+# `catch_warnings()` block seeded from the ini filters, which discards anything
+# registered at conftest import time.
+def pytest_configure(config):
+    try:
+        from starlette.exceptions import StarletteDeprecationWarning as _W
+    except Exception:  # pragma: no cover - starlette absent or too old to have it
+        return
+    config.addinivalue_line("filterwarnings", f"ignore::{_W.__module__}.{_W.__qualname__}")
+
+
 def pytest_report_header(config):
     """Make the resolution decision visible in the test header."""
     spec = importlib.util.find_spec("qector_decoder_v3")