Expand error status test coverage

- Added explicit status validation across error handling tests.
- Added lifecycle and slot-leak checks to older tests.
- Improved unhandled-error propagation coverage.
- Added repository guidance and a test runner script.
- Verified all 23 CTest tests pass.

Co-Authored by Codex GPT 5.4

tests/err_catch.c

@@ -1,4 +1,5 @@
 #include "akerror.h"
+#include "err_capture.h"
 
 akerr_ErrorContext *func2(void)
 {
@@ -31,6 +32,11 @@ int main(void)
     } CLEANUP {
     } PROCESS(errctx) {
     } HANDLE(errctx, AKERR_NULLPOINTER) {
-      akerr_log_method("Caught exception");
+        AKERR_CHECK_STATUS(errctx, AKERR_NULLPOINTER);
+        akerr_log_method("Caught exception");
     } FINISH_NORETURN(errctx);
+
+    AKERR_CHECK(akerr_slots_in_use() == 0);
+    fprintf(stderr, "err_catch ok\n");
+    return 0;
 }