test: accept empty skip reasons

docs/test-system-v2.md

@@ -235,6 +235,21 @@ work never caches a test result. A directly invoked retained binary exposes the
 warning on stderr and accounting on stdout because no coordinator combines its
 descriptors or emits a package result.
 
+The shared language runtime accepts `test.skip("")` as a successful skip. Its
+zero-length reason is a structurally valid skipped control result, so a normal
+zero child exit produces the existing `qualified.name ... SKIP: ` line followed
+immediately by newline, increments skipped accounting, and contributes neither
+a failure nor a harness error. Later selected tests continue. This one runtime
+classification covers raw single-file, same-package, external-test, and honest
+test-only descriptors, an active-test call reached through production package
+code, filtered execution, coordinator-run retained binaries, and later direct
+retained-binary execution. Production files still define no test-body
+descriptor. Nonempty skips are unchanged; an oversized reason is still an
+invalid harness result, and skip outside an active test still aborts. List mode
+still executes no body. This rule does not merge per-test children or change
+package/import initialization, product scheduling, timeout and process-group
+ownership, publication, persistence, or cleanup.
+
 Directory test binaries are always linked under the coordinator's temporary
 product root. The retained-output option has the exact registered name `o` and
 accepts `-o VALUE`, `--o VALUE`, `-o=VALUE`, and `--o=VALUE`. An equals form