Deterministic trig: pin error budget + deterministic oracle for audit test

[flyingrobots]

Background:

• crates/warp-core/tests/deterministic_sin_cos_tests.rs contains test_sin_cos_error_budget_wip, currently #[ignore] because it compares against platform libm-derived f64 trig.

Goal:

• Replace the reference/oracle with a deterministic one (or a pinned golden-vector oracle) and establish an explicit, documented error budget for the LUT-backed warp_core::math::trig backend.

Exit criteria:

• Define and document acceptable max ULP / absolute error for sin and cos over a specified domain (e.g. [-2TAU, 2TAU]).
• Implement deterministic measurement that does not depend on host libm (e.g. precomputed vectors or a deterministic polynomial reference).
• Un-ignore the test (or split into deterministic golden + optional audit).

Notes:

• Determinism requirement: sin(-x) must be the exact bitwise negation of sin(x); cos(-x) must match cos(x).

[flyingrobots]

Opened PR #182 (stacked on PR #167) to un-ignore the trig error-budget test using a deterministic libm oracle and pinned thresholds.