test: port 915/949 module-global access carriers to corpus fixtures

915_arr_module_index_run.c -> r915_arr_mod_idx0 (run), r915_arr_mod_
  idx2 (run-exit 1), r915_arr_mod_idx4 (run-exit 6); the single-file
  rows were already owned by r915_arr_local_* + test-data-byteid.
949_xmod_fnptr_const_run.c -> r949_xmod_fnptr_const_table (run),
  r949_xmod_fnptr_wrong_sig, r949_xmod_fnptr_nonfn_dotted (error
  'not assignable' both stages).

The 915 module rows upgrade from 994-delegated to per-fixture cs==ww
byte identity; 949's 2-file -I tree was not load-bearing — inline
packages exercise the same N_DOT &mod.fn mangle (mafn(leaf, module)).

test/wcc/data/r915_arr_mod_idx0/case.ww

@@ -0,0 +1,10 @@
+//ww:run
+// migrated from test/wcc/915_arr_module_index_run.c: cross-package mod.arr[0] — LEAQ base + u16 load width (#128b).
+package wcmodarr;
+export let probe_table: [8]u16 = [0u16, 0x0800u16, 0x0801u16, 0x0803u16, 0x1006u16, 0x1009u16, 0x100Du16, 0x1812u16];
+package main;
+import wcmodarr;
+export fn main() i32 = {
+	let v: u32 = (wcmodarr.probe_table[0]: u32);
+	return v: i32;
+};