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 type-fn head visibility check (`headFnLeak`) used the module-scope
NAME predicate `isNameVisible`, so a same-name 1-hop NON-function (a value
const `Make :: 123`) reported the name "visible" and let the global
`fn_ast_map` type-fn — whose real author is 2 flat hops away — silently
instantiate. `size_of(Make(s64))` printed 8 at exit 0 instead of a
visibility diagnostic.
Decide visibility from the ELIGIBLE FUNCTION authors directly reachable
from the use site (`flatFnAuthorVisible`, mirroring `flatFnAuthorAmbiguous`'s
fn-only author view): visible iff the own author or a 1-hop flat-import
author is a `fn_decl`. A non-function does not vouch. Guarded to fall open
when the import facts aren't wired (comptime / directory imports), mirroring
`headTypeGate`. Own / scope-local / 1-hop / directly-imported type-fn heads
still resolve; 0769 ambiguity unchanged.
Regression: examples/0770-modules-type-fn-head-non-transitive (main → b
[`Make :: 123` + flat-imports c] → c [`Make :: ($T) -> Type`]); the bare
`Make(s64)` head emits "type 'Make' is not visible", exit 1.
