lang: array-typed '::' consts as immutable globals (PLAN-CONST-AGG step 1)

K : [4]s64 : .[...] and the untyped A :: .[1, 2, 3] register as
is_const globals: one storage, reads GEP it, dead-global elimination
drops unused ones, source-aware reads come free via selectGlobalAuthor.

- registerConstArrayGlobal (scanDecls pass 2): typed via the annotation
  (array-ness + dimension/count checked), untyped via element-type
  unification — all ints s64; ANY float promotes the element type to
  f64 with ints converting exactly; bool/string homogeneous; a
  non-numeric mix or non-inferable element asks for an annotation.
- constExprValue converts int elements into float destinations exactly
  (the int+float promotion rule, element-wise).
- emitGlobals marks is_const globals LLVMSetGlobalConstant — also flips
  the comptime-backed #run globals and __sx_default_context to
  'constant' (37 pinned IR snapshots regenerated; runtime unchanged).
- Element shapes: nested arrays, struct elements, strings, bools.
  Non-constant elements / dim mismatch / mixed types diagnose loudly.

Examples: 0177 (feature matrix incl. @K reads through *[4]s64 — needs
the 0117 fix), 1159/1160/1161 (diagnostics), 0837 repointed to values.

examples/0837-modules-array-const-no-cross-borrow.sx

@@ -1,11 +1,11 @@
-// An ARRAY-typed `::` const (`K : [4]s64 : .[...]`) is not a supported
-// module-const shape — its own module's read diagnoses cleanly as
-// unresolved. The own author OWNS the name: the read must never borrow
-// another module's same-named scalar const (which used to type `K[2]`
-// against the scalar and panic at LLVM emission).
+// An ARRAY-typed `::` const is an immutable global owned by its module.
+// Cross-module: the main file's scalar `K : s64 : 4` and h.sx's array
+// `K : [4]s64 : .[...]` coexist — each module's bare `K` binds its OWN
+// author (h's use_k reads ITS array, main's K stays the scalar 4).
 //
-// Regression (issue 0115). When array `::` consts land, repoint this
-// example at the new behavior.
+// Regression (issue 0115): h.sx's read used to borrow main's scalar K
+// and panic at LLVM emission; before array consts landed (PLAN-CONST-AGG
+// step 1) the shape was a clean "unresolved" diagnostic.
 
 #import "modules/std.sx";
 h :: #import "0837-modules-array-const-no-cross-borrow/h.sx";
@@ -13,5 +13,5 @@ h :: #import "0837-modules-array-const-no-cross-borrow/h.sx";
 K : s64 : 4;
 
 main :: () {
-    print("{}\n", h.use_k());
+    print("{} {}\n", K, h.use_k());
 }