fix(store): address QA round 2 findings

- Validate child exit status (WIFEXITED + WEXITSTATUS) after waitpid so
  the test fails fast if the child couldn't open the store, rather than
  passing vacuously due to the "crashed" row never being written

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: shanemccarron-maker

tests/test_store_bulk.c

@@ -141,6 +141,8 @@ TEST(bulk_crash_recovery) {
     ASSERT_GT(pid, 0);
     int status;
     waitpid(pid, &status, 0);
+    /* Confirm child exited normally so the write actually occurred. */
+    ASSERT(WIFEXITED(status) && WEXITSTATUS(status) == 0);
 
     /* Recovery: database must open cleanly. */
     cbm_store_t *recovered = cbm_store_open_path(db_path);