Phase 1: /lib/complex + wire %cplx into Lagoon

[sigilante]

Implements Phase 1 of the %cplx design (lagoon/CPLX-DESIGN.md, PR #45):
complex-number arrays with a SoftBLAS-interleaved atom layout, element-wise
ops, and complex linear algebra. Unblocks Saloon eigenvalues/eigenvectors.

/lib/complex (pure Hoon)

cs (@cs = two @rs) and cd (@cd = two @rd) doors keyed on rounding
mode. Packed atom = real low / imag high, matching SoftBLAS complexN_t
(validated on ~hex: (1+2i)·(3+4i) = -5+10i). Arms: add/sub/mul,
div (Smith's algorithm), neg, conj, abs (hypot, returns real-valued
complex), equ/neq (bit equality). No total order — no gth/lth.

Lagoon (sur + lib)

• %cplx in the kind union; bloq 6=cs 7=cd (meta.tail unused).
• fun-scalar: add/sub/mul/div, equ/neq → complex one/zero;
  gth/gte/lth/lte crash (complex is unordered).
• New %conj op (identity on real kinds, so dotc ≡ dot there);
  trans-scalar %abs/%conj.
• New ray arms conj and dotc (Hermitian inner product
  Σ conj(aᵢ)·bᵢ). Bilinear dot, mmul, cumsum use the generic
  round-each-step path (no exact complex accumulator).
• get-term → @c aura terms (%cs/%cd); eye/ones constant 1+0i;
  scale raw-pack; change out of complex refuses (lossy).

Tests — all green on ~hex

• /tests/lib/complex (4): cs/cd arith, unary, compare.
• /tests/lib/lagoon-cplx (7): arith, unary (abs/conj), compare, ones,
  cumsum, dot (-18+68i) vs dotc (70-8i), complex mmul.
• Regressions: %unum (14) and %int2 (5) still pass.
• Oracle: tools/complex_check.py (NumPy complex64/complex128).

Not in scope (per design)

Jets (Phase 2: add *dotu/cgemm/zgemm to our SoftBLAS); Saloon eig
(Phase 3); @ch/@cq widths; change into-complex.

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