The slice-IDENT call-arg fast path pushed the header words off off(BP)
where off=localfind(name); for a module-global slice localfind→0, so it
read saved-BP/RIP/caller garbage instead of name(SB). Add the global
branch (LEAQ name(SB) base, push 16/8/0 off it) mirroring the sibling
N_SLICE arm; local path unchanged. cstage-only: wwstage checker-rejects
the shape (#120), so byte-id-safe and the twin defers to #125. Unblocks
path c2-stack (dot/dotdot are faithful module-global []u8). Sibling
structarg fast-path filed #150.
