  We examine Lyman continuum (LyC) leakage through H II regions regulated by
turbulence and radiative feedback in a giant molecular cloud in the context of
fully-coupled radiation hydrodynamics (RHD). The physical relations of the LyC
escape with H I covering fraction, kinematics, spectral hardness, and the
emergent Lyman-$\alpha$ (Ly$\alpha$) line profiles are studied using a series
of RHD turbulence simulations performed with RAMSES-RT. The
turbulence-regulated mechanism allows ionizing photons to leak out at early
times before the onset of supernova feedback. The LyC photons escape through
turbulence-generated low column density channels which are evacuated
efficiently by radiative feedback via photoheating-induced shocks across the
D-type ionization fronts. Ly$\alpha$ photons funnel through the photoionized
channels along the paths of LyC escape, resulting in a diverse Ly$\alpha$
spectral morphology including narrow double-peaked profiles. The Ly$\alpha$
peak separation is controlled by the residual H I column density of the
channels and the line asymmetry correlates with the porosity and multiphase
structure of the H II region. This mechanism through the turbulent H II regions
can naturally reproduce the observed Ly$\alpha$ spectral characteristics of
some of LyC-leaking galaxies. This RHD turbulence-origin provides an appealing
hypothesis to explain high LyC leakage from very young ($\sim3$ Myr)
star-forming galaxies found in the local Universe without need of extreme
galactic outflows nor supernova feedback. We discuss the implications of the
turbulent H II regions on other nebular emission lines and a possible
observational test with the Magellanic System and local blue compact dwarf
galaxies as analogs of reionization-era systems.
