[test] fix: register internal pytest marker

[yaoyu-33]

Summary

• Fixes the main / mcore-main automated bump PR chore(beep boop 🤖): Bump uv.lock (main, mcore-main) (2026-06-15) #4357 by registering the existing internal pytest marker.
• The fix is limited to pytest marker configuration; no MCore compatibility guard is added.

Original bump PR: #4357
Target: main
Failure classification: Bridge broke itself

Root Cause

Launch_Unit_Tests_Core collected tests/unit_tests/models/qwen_vl/modelling_qwen3_vl/test_attention.py, which uses @pytest.mark.internal. The project runs pytest with --strict-markers, but pyproject.toml did not register internal, so collection failed before MCore-specific coverage ran.

Fix

• Add internal to [tool.pytest.ini_options].markers.

Guards

None added or removed.

Validation

• uvx --from pytest==9.1.0 pytest -c /tmp/mb_pyproject_before_4357.toml --override-ini addopts=--strict-markers /tmp/mb_internal_marker_repro.py --collect-only -q: failed before the fix with internal missing.
• uvx --from pytest==9.1.0 pytest -c pyproject.toml --override-ini addopts=--strict-markers /tmp/mb_internal_marker_repro.py --collect-only -q: passed after the fix, 1 test collected.
• CW interactive partition, standard Bridge container: uv run python -m pytest tests/unit_tests/models/qwen_vl/modelling_qwen3_vl/test_attention.py -v: passed, 1 passed, 33 warnings in 1.25s.
• CW interactive partition, standard Bridge container: uv run pre-commit run --all-files: passed.

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[yaoyu-33]

/ok to test 9397e03

[yaoyu-33]

/ok to test 8565d45

[claude]

Light Code Review

Summary: Registers the internal pytest marker that was missing from pyproject.toml, fixing --strict-markers collection failures in CI. Also bumps MCore submodule and regenerates the lockfile.

The fix is correct and minimal. The @pytest.mark.internal usage in tests/unit_tests/models/qwen_vl/modelling_qwen3_vl/test_attention.py:129 is the only site using this marker, and the new registration in pyproject.toml resolves the strict-markers error.

No issues found.

Minor observations (non-blocking):

• wrapt moved from stable 2.2.1 to RC 2.2.2rc1 and nvidia-cutlass-dsl from 4.5.2 to 4.6.0.dev0 in the lockfile. This is expected given prerelease = allow in pyproject.toml, but worth noting in case either introduces regressions.
• pytest bumped from 9.0.3 to 9.1.0 (minor version) -- unlikely but possible source of behavior changes in test collection/execution.

Suggested test cases: No perf tests impacted.

[yaoyu-33]

/ok to test 09511e3

[yaoyu-33]

/ok to test f706d1d

[yaoyu-33]

/ok to test 6e553da