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.
The static-method-call head `Box(s64).make(7)` was the last uncovered bare-
generic-head instantiation site: it gated visibility with `headTypeLeak` but
then instantiated the global last-wins `struct_template_map` entry and ran the
name-keyed `Box.make` from `fn_ast_map`, so a NON-visible 2-flat-hop same-name
template (and its method) won. `size_of(Box(s64))` picked the visible `b.Box`
(8) while `Box(s64).make(7)` returned a `c.Box`-shaped (16) value.
Route the static-method head through the single bare-VISIBLE author for BOTH
the instantiated type layout AND the method body: split the existing visible-
author selection into `bareVisibleStructDecl` (returns the StructDecl + source;
single selection point, `bareVisibleStructTemplate` now delegates to it — no
drift) and source-pin the method body via the author's own `sd.methods`
(`structMethodFn`) instead of the last-wins `fn_ast_map`. Ambiguity (>1 visible
author) is already diagnosed by the pre-existing `headTypeLeak` gate.
Exhaustive bare-head instantiation-site audit (all callers reaching
`instantiateGenericStruct` / `struct_template_map` for a bare head): .call alias,
.parameterized_type_expr alias, resolveType .call, resolveTypeCallWithBindings,
resolveParameterizedWithBindings — all already route through the visible-author
selection; the static-method head was the only remaining one and is now covered.
Regression 0776: bare generic static-method head with a 2-hop same-name template
asserts the visible author's layout (xtype=8, x reachable); fail-before xtype=16.
