lock(reify): meta.sx surface + bodyless #builtin decls + loud bails

REIFY Phase 0.0. Add the comptime type-metaprogramming surface as the
on-demand module modules/std/meta.sx (NOT the prelude — declaring its
data types in always-loaded core.sx interns them into every module's
type table and shifts every .ir snapshot):

  - EnumVariant / EnumInfo / TypeInfo data types. TypeInfo's variant uses
    the backtick raw escape `enum so it reads as the keyword.
  - reify / type_info / field_type as bodyless #builtin decls.

Each builtin bails LOUDLY when reached unimplemented (no silent default):
  - reify(...) in a :: type-alias position -> decl.zig .call branch
    (also the Phase 0.2 construction hook); poisons the alias .unresolved.
  - reify / field_type in any other type position ->
    generic.zig resolveTypeCallWithBindings.
  - type_info(...) in expression position -> call.zig tryLowerReflectionCall.

Unit test src/parser.test.zig (registered in root.zig) locks that the
decls parse. zig build test green (447 unit, 669 examples).

src/ir/lower/decl.zig

@@ -651,6 +651,17 @@ pub fn scanDecls(self: *Lowering, decls: []const *const Node) void {
                         .field_access => |fa| fa.field,
                         else => "",
                     };
+                    // `E :: reify(...)` — mint a nominal type from a `TypeInfo`
+                    // and register `E` as an alias to it. The interpreter-side
+                    // construction lands in Phase 0.2; until then bail LOUDLY
+                    // and poison `E` to `.unresolved` (so downstream `E.value`
+                    // gets a clean follow-on, not a silent default type).
+                    if (std.mem.eql(u8, callee_name, "reify")) {
+                        if (self.diagnostics) |d|
+                            d.addFmt(.err, cd.value.span, "reify is not yet implemented (REIFY Phase 0.2)", .{});
+                        self.putTypeAlias(self.current_source_file, cd.name, .unresolved);
+                        continue;
+                    }
                     // A namespaced callee (`ns.Box(..)`) is an explicit qualified
                     // reach, exempt from the bare-head visibility gate (E4).
                     const head_qualified = call_data.callee.data == .field_access;