Extends generate/math_versor_arithmetic.py with one new function:
def subtract(addend: float) -> np.ndarray:
return translator(-float(addend))
Single-line delegate to translator(); no new algebra.
Adds tests/test_arithmetic_subtract_and_group.py covering all nine
ADR-0140 acceptance families:
Families 1-6 (ADR-0139 families applied to subtract):
1. Embedding well-formedness — null cone preserved for subtract cases
2. Translator-of-negative well-formedness — versor_condition < 1e-6
3. Closure — sandwich result stays on null cone
4. Arithmetic correctness — decoded value == a − b within 1e-9
5. Replay determinism — byte-identical across runs
6. Composability — subtract(c) ∘ subtract(b) decodes to a − b − c
New group-property families (structural verification of ADR-0139 claim):
7. Inverse composition — T_{-b} * T_b = identity (max residual: 0.000e+00)
8. Round-trip closure — versor_apply(T_{-b}, versor_apply(T_b, X)) → (a, u)
9a. Sum composition — T_a * T_b = T_{a+b} (max residual: 0.000e+00)
9b. Commutativity — T_a * T_b byte-equals T_b * T_a (all 10 cases)
All 96 tests pass. Group residuals are exactly 0.0 in float64.
The additive subgroup of Cl(4,1) translators along e1 is abelian and
closed; ADR-0139's algebraic claim holds at the group level.
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