v0.2.0

The demo release: the tracer handles the code real demos are made of.

• In-place operations land: -=, out=, views with write-back; every Pair owns its buffer
• Chained matmuls over scatter-built matrices (C.T @ R @ C traces to closed forms)
• Sparse diagonal matrices trace: diags_array as structured allocation, .diagonal/.tocsc on traced values
• Fold symbols never leak: certificates reference only defined terms, enforced at harvest
• Contracts for the everywhere-atoms: svd, qr, cholesky, lstsq, pinv, fft checked against their defining equations per call
• Random draws seal as sympy.stats variables; E and Var of results in closed form
• skverify.latex renders code-ish names and matrices cleanly
• Two executed demos: a 20-page scipy spline derivation checked symbolically, and sklearn 1.9's BayesianRidge fix read from certificates