[aarontrowbridge]

Closes #24

One line: the version bump that puts a working substrate in front of fresh consumers.

• The registered 0.2.0 tarball is broken in fresh resolutions under NamedTrajectories >= 0.9.3 (the Piccolo duration collision, Piccolo.jl #323 in flight); 0.3.0 binds duration from its defining module and is immune.
• Carries since 0.2.0: the Sosia twin core (Absorb the Sosia twin core (drift, records, truth/belief contract) #18), the weakdeps extension split (Weakdeps split: Piccolo and PythonCall become package extensions #19), TwinSoc (TwinSoc: the twin's soc face (imperfect response, drifting truth) #23), and the runner-rotation golden repair (captured-value goldens now isapprox-tight; within-process pins stay exact).

Release notes are posted with the registration comment at merge.