fix: Python 3.14 compatibility and test suite correctness

[blshkv]

Summary

This PR fixes 8 bugs that make VULTURE fail on Python 3.14 and break the test suite on all Python versions. Every issue was found during packaging for the Pentoo Linux overlay and tested deeply — the full suite runs 63 passed, 2 skipped on Python 3.14.7 after these changes.

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1. Python 3.14 — sys.modules registration missing before exec_module (3 files)

chemical_rf/__init__.py, forensics/__init__.py, lab/__init__.py all load a legacy .py sibling via importlib without registering the module in sys.modules first. Python 3.14 changed dataclasses._is_type to look up cls.__module__ in sys.modules; without the registration every @dataclass in those modules raises TypeError.

Fix: sys.modules[_spec.name] = _legacy before exec_module.

2. materials.py — reflection_coefficient undefined, absorption_coefficient broken

absorption_coefficient calls reflection_coefficient which doesn't exist in the file → NameError on import. __init__.py and pipeline.py also import reflection_coefficient by name.

Fix: add reflection_coefficient as (Z_L - Z_0) / (Z_L + Z_0) and rewrite absorption_coefficient as 1 - abs(gamma)**2.

3. cli.py — lab_cli imported but never registered

from vulture.lab_cli import lab_cli is present but cli.add_command(lab_cli, name="lab") is missing → vulture lab silently unavailable.

4. physics_laboratory.py — wrong dict key; dead instance methods cause infinite recursion

• calculate_link_budget returns 'margin_db' but all callers expect 'link_margin_db'.
• Three instance methods on RadarSimulator are defined after the correct @staticmethod implementations. Each returns a lambda immediately (unreachable code below), and the final duplicate calculate_radar_range shadows the static version and recurses infinitely.

5. fingerprint.py — rfft rejects complex input; dead code raises ValueError

• np.fft.rfft on complex64 IQ data raises TypeError — should be np.fft.fft / np.fft.fftfreq.
• Two dead lines in similarity() cast hex SHA-256 strings to np.uint8 → ValueError; variable d is never used.

6. timeseries_engine.py — circular buffer returns empty slice after full write

add_data was missing the n >= buffer_size case. After filling the buffer it set position = 0, so buffer[:position] returned an empty array. Fix: set position = buffer_size and add an explicit branch for the overflow case.

7. pytest.ini — contains a Python docstring, not an INI section

The file held """Pytest markers…""" — a string literal pytest silently ignores. Replaced with [pytest].

8. tests/conftest.py — conftest_enterprise.py never auto-loaded

pytest only discovers files named conftest.py. All fixtures in conftest_enterprise.py (bpsk_signal, qpsk_signal, chirp_signal, burst_signal, multipath_signal) were invisible to the test runner. Merged into conftest.py and extended base fixtures to the sizes the enterprise suite requires.

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Test result: 63 passed, 2 skipped on Python 3.14.7 (was: import errors + multiple test failures before this patch).

SPDX-License-Identifier: AGPL-3.0-only

[black-221]

Ok good

[hatraa757-cpu]

Good

[black-88888]

I might accept, but I'm not sure.