Move device-specific content (hardware, software, libraries) from
TOOLCHAIN.md into new docs/rg35xx-plus.md. Add partition layout,
full boot chain trace (systemd → launcher.sh → loadapp.sh → dmenu_ln),
and sdlamp2 deployment instructions via dmenu_ln config toggle.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
