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 bare-fn-as-value site (func_ref / fn-ptr / closure coercion) eagerly
lazily-lowered the name-keyed first-wins WINNER before the resolveBareCallee
block could reroute a genuine flat same-name collision to its per-source
author. Taking a SHADOW author's fn value therefore lowered (and could
mis-diagnose) the unused winner's body. Move lazyLowerFunction INSIDE blk_fv
onto the `.none` fallback only, mirroring the closure(fn) and free-function
UFCS sites: on `.func` use the resolved author's FuncId and never touch the
winner; on `.none` fall through to lazy-lower + resolveFuncByName the winner.
Regression: examples/0735-modules-flat-same-name-fn-value-winner — the
first-wins winner's body is independently broken and never used; a shadow
taken as a function value binds the shadow and runs (exit 0) while the winner
is not lowered. Fails-before (unresolved symbol in the winner), passes-after.
