Closes the remaining three F0.6 findings so the universal backtick raw
identifier holds in BOTH classifiers and at EVERY parser construction site.
1. Struct-body constants thread is_raw + name_span. The struct-body const
forms (untyped `` `s2 :: 5 `` and typed `` `s2 : T : v ``) built the
const_decl node without name_span/is_raw, so a backtick const was falsely
rejected and a bare reserved-name const caretted at 1:1. They now capture
both. Structural cure: `ast.ConstDecl`'s name_span + is_raw carry NO
default, so the compiler rejects any construction site that omits them
(mirrors checkBindingName's required `is_raw` arg). FnDecl keeps its
defaults — every parser fn_decl routes through parseFnDecl whose
`name_is_raw` is a required parameter (equivalent guarantee).
2. Raw identifier in TYPE position flows through the normal continuations.
parseTypeExpr no longer returns a terminal type_expr for a raw atom; the
raw flag rides the atom through the qualified-path / Closure / parameterized
continuations, so `` `s2(s64) ``, `` *`s2 ``, `` ?`s2 `` all parse.
ParameterizedTypeExpr carries is_raw; resolveParameterizedWithBindings
skips the `Vector` intrinsic when raw.
3. sema/LSP (the second classifier) honors is_raw. Type.fromTypeExpr returns
null for a raw type_expr; resolveTypeNode skips the builtin classifier when
raw; resolveTypeNameStr takes a skip_builtin arg threaded from te/id.is_raw
(compound inner names pass false). A backtick reserved-name annotation now
resolves to the user type in the editor index, not the builtin.
Tests: examples/0156 (struct-body const), 0157 (parameterized raw type +
wrappers), 1142 (bare struct-body const errors, caret on name); src/sema.test.zig
pins the LSP raw-type resolution (fail-before verified). Gate: 365 unit tests,
429 examples, 0 failed.
