v0.3.0

The testing release: the spec from the paper, checked as a test.

• skverify.testing lands: @specifies turns a formula into a pytest test, check_formula returns the Verdict behind it
• Verdicts are four-tier, never a bare boolean -- exact, float-constant, sampled, differs/undecided/incomplete -- each carrying the shape it was decided at, and a counterexample when it fails
• Guard-aware sampling: sampled points respect the traced branch conditions, so the sampled tier is honest about what it actually checked
• Real scipy specs across five modules in the suite, including the known refusals (pearsonr, iqr) pinned at the incomplete tier
• np.prod reductions, and 2D np.gradient with repeated axes rejected the way numpy rejects them
• 7x faster traces on loop-heavy code
• Sphinx docs on Read the Docs; numpydoc docstrings across the public API
• skverify-hypothesis is gone -- one testing story. The skverify_hypothesis module that shipped in 0.2.0 is no longer in the wheel.