Supersedes the defunct hs.2 plan at 8ca602d (runtime-sentinel +
Str-in-ADT drop safety). After the spec amendment at 2a72a4a dropped
the sentinel-rc-header story, the iter scope is now a surgical retrofit
of hs.1's emission: drop the leading i64 sentinel slot from static-Str
globals, land the IR-Str pointer on the (now first) len-field via
GEP (i32 0, i32 0). The four +8 consumer GEPs are invariant across the
switch. Three tasks: (1) update the two IR-shape tests to the new
layout (RED); (2) flip three format-string sites + two doc-comments
in lib.rs (GREEN); (3) regenerate hello.ll snapshot + workspace +
cross_lang + compile_check + check.
Brummel
51a096cf83