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 reserved-type-name binding diagnostic fired correctly but underlined the
enclosing statement / if / while / for / match / protocol / #objc_class block
because every binding-name check reused the parent `node.span`.
Thread each binding name's own span through the AST and parser, and pass it to
`checkBindingNames`:
- ast: add name spans to VarDecl, DestructureDecl, If/WhileExpr, ForExpr
(capture + index), MatchArm, Catch/OnFailStmt, Protocol/ForeignMethodDecl.
- parser: populate each span at the binding site from the name token's loc;
destructure reuses each target identifier's own span.
- semantic_diagnostics: every checkBindingName call now passes the binding's
own span — no site falls back to node.span. fn/lambda params already used
Param.name_span.
Carets now land on the offending identifier itself. New regression
examples/1125 asserts the protocol default-body and sx-defined #objc_class
method param spans; 0125/1119-1124 expected updated to the precise carets.
