The global state becomes struct blk_chain, reached through a current
pointer: blk_chain_default, blk_chain_new, blk_chain_select. Nothing
that uses the one chain changes. blk_subsys_init loses its VM argument,
which was stored and never used. docs/v4.0.0/MESH.md 8.4.
Accepted on the v3 configuration: amd64, aarch64 and riscv64 reach the
zuse prompt, no UNKNOWN WORD, PARITY:M7.1a hash 0x08873e0f44b7cb2a on
all three, as on 2026-10-03. logs/20261006-202918, -203036, -203230.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
