Surface rename of the signed integer family: s1..s64 become i1..i64
(u1..u64, usize, isize unchanged). 'string' keeps the s-prefix arm in
name classification; width parsing moves to the i-prefix arm next to
isize.
Internal TypeId tags follow the surface (.s8/.s16/.s32/.s64 ->
.i8/.i16/.i32/.i64), as do mono-key mangle fragments (ptr_i64,
tu_i64_bool) and all display/diagnostic formatting (i{d}).
Migrated in the same sweep: stdlib + examples + issue repros + FFI C
companions (shared symbol names like ffi_id_i64), expected
stdout/stderr/ir snapshots, specs.md, readme.md, CLAUDE.md/AGENTS.md,
implementation_plan.md, docs/, issue writeups. Vendored stb_image and
historical flow state left untouched.
zig build test: 426/426; examples suite: 595/595.
A qualified generic type head `ns.Box(args)` was stripped to its bare name and
read from the last-wins `struct_template_map`, so the namespace qualifier never
selected the template author: `a.Box(s64)` and `b.Box(s64)` (two namespaces each
authoring a same-name `Box($T)` with different layouts) both instantiated the
global same-name template. The documented ambiguity escape hatch ("qualify it as
ns.Box") silently produced the wrong layout.
Select the template via the namespace edge (importer -> alias -> NamespaceTarget)
instead of the bare map, at both the .call and parameterized-type-expr head
sites. Two same-name templates instantiated with the same args would also collide
on the mangled name `Box__s64`, so tag the non-canonical author's mangled name
with its source (the canonical bare-map author keeps the untagged name -> no
churn for single-author generics).
Extract `buildGenericStructTemplate` so the bare registration and the new
namespace-qualified selection share one template builder.
Regression: examples/0772 — two namespaces each authoring Box($T) with different
layouts; ns_a.Box(s64) and ns_b.Box(s64) resolve to their own module's template
(sizes 8 and 16). Fail-before on 566de96 (a=16 b=16), pass-after (a=8 b=16).
