[autodev] fix csv_reporter --csv collision with pytest-csv

Subprocess-spawned tests in e2e/_unit_tests/reporting/ crashed with
"argparse.ArgumentError: argument --csv: conflicting option string: --csv"
because pytest-csv (autoloaded via entry-point) and our custom plugin both
register --csv. pytest's option registry does not allow overrides.

Fix: drop pytest-csv from e2e/runner/requirements.txt. It was unused, dead
weight, and incompatible with pytest 9.x (uses removed hookwrapper marker).
Update conftest + csv_reporter comments to match.

After fix: 1229/1229 in e2e/_unit_tests pass.

Bug ticket creation deferred (user skipped interactive Q this session) —
payload recorded in _docs/_process_leftovers/2026-05-17_csv_reporter_*.md
for replay on next /autodev.

Co-authored-by: Cursor <cursoragent@cursor.com>

e2e/runner/requirements.txt

@@ -5,13 +5,17 @@
 #     depend on gtsam — the numpy<2 ABI block that forces the SUT pin does not
 #     apply here; see _docs/_process_leftovers/2026-05-11_d_cross_cve_1_opencv_pin_deferred.md).
 #   - Versions match the SUT pyproject where feasible (numpy 1.x line, pyproj 3.6+, pydantic 2.x).
-#   - pytest 8.x is the stable line; pytest-csv 3.x supplies the columns the CSV reporter plugin extends.
+#   - pytest 8.x is the stable line. We do NOT depend on pytest-csv: an earlier
+#     design considered extending its column hooks, but our custom
+#     `runner.reporting.csv_reporter` plugin owns the `--csv` / `--csv-columns`
+#     CLI surface end-to-end and pytest-csv 3.x conflicts on the flag name and
+#     is also incompatible with pytest 9.x (uses the removed `hookwrapper`
+#     marker). Keep it out of the image.
 
 pytest>=8.0,<9.0
 pytest-timeout>=2.2,<3.0
 pytest-xdist>=3.5,<4.0
 pytest-forked>=1.6,<2.0
-pytest-csv>=3.0,<4.0
 
 # MAVLink ground side — used for both AP signing-handshake assertions and the
 # passive listener that consumes mavproxy-listener's forwarded UDP stream.