wcc: reject module-scope alloc/call let initializers at check time

A module-scope let whose rhs runs code (alloc, call — peeled through
cast/?/! wrappers) emitted no DATAW slot: emit_lets' fold-fail
silently skipped the definition and every reference died at LINK
time with 'undefined reference', the one unacceptable failure mode
(rule 7). Hare's model rejects at check time (ref/harec/src/
check.c:4360 'Unable to evaluate initializer at compile time') and
routes runtime init through @init, which ww does not have — so both
frontends now reject at the declaration with identical wording.

alias_infptr_global flips compile->error as the alloc pin (its
letvartnode N_TPTR-over-N_TSTRUCT coverage lives on in the local
alias_infptr_{nest,slicecap} siblings); callinit_global_reject pins
the call shape. Corpus pin 1741/345/21/209/1166/3482.

test/wcc/data/alias_infptr_global/case.ww

@@ -1,6 +1,10 @@
-//ww:compile
-// INFERRED-global *struct root: the letvartnode gate must accept the
-// checker-synthesized N_TPTR-over-N_TSTRUCT exactly as the local arm.
+//ww:error "runtime initializer unsupported (alloc/call; rule 7)"
+// Module-scope alloc initializer: no DATAW slot exists for a
+// runtime-computed global, so pre-reject every reference died at
+// LINK time ("undefined reference to 'main.gp'") — the checker now
+// rejects at the declaration on both frontends (Hare model:
+// ref/harec/src/check.c:4360 rejects non-compile-time-evaluable
+// global initializers; ww has no @init path).
 package main;
 type box = struct { s: str, n: int };
 let gp = alloc(box { s = "hi", n = 1 })!;

test/wcc/data/callinit_global_reject/case.ww

@@ -0,0 +1,7 @@
+//ww:error "runtime initializer unsupported (alloc/call; rule 7)"
+// The call sibling of alias_infptr_global's alloc reject: a
+// module-scope call initializer has no link-time data either.
+package main;
+fn mk() i64 = { return 7; };
+let gc: i64 = mk();
+export fn main() i32 = { return gc: i32; };