Two-column layouts left an unbalanced empty gap for this content (Node/RPC vs
Security+Daemon can't be evened into two columns), so drop the split entirely:
Node -> RPC -> Security -> Daemon Binary now stack vertically at full card width.
This guarantees no horizontal gap and gives the RPC grid and the Daemon Binary
button rows the full width they want.
Implemented by forcing the existing vertical-flow path (`stacked`) always on, so
the section bodies are unchanged; removes the now-unused column-split math and the
node-sec-stack-width schema key.
Full-node + lite build clean; source hygiene clean.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>