A str field reached through a chained dot (o.i.s) emitted two loads
(ptr, len) and stored a stale CX as the cap — both stages, at any
non-zero chain depth. Emit the full header at the chained-dot leaf.
Review item #29.
Both stages move in one commit: one emission contract; splitting
would leave the byte-id gates red between the halves.
Reading a slice-typed tuple element (t.0) loaded only the pointer
word; len and cap took whatever was left in BX/CX — silent garbage in
BOTH stages once anything clobbered the registers between build and
read. Load all three header words at the tuple-element arm. Review
item #28.
Both stages move in one commit: one emission contract; splitting
would leave the byte-id gates red between the halves.
Casting a global str to []u8 dropped the cap=len synth (the trailing
MOVQ BX,CX) — the synth was gated on a local-ident source shape.
Key it on the source type so local/global/field/call sources all get
the header. Review item #19.
