ww imports: require imports before declarations

docs/test-system-v2.md

@@ -402,6 +402,19 @@ directory entry order. A recursive pattern omits a directory with no eligible
 source, while an explicit wrong-target-only build rejects it as having no WW
 package source. There is no source-level build-expression or user-tag mode.
 
+Within every eligible production, same-package test, external-test, or
+test-only source, the package clause is followed by one contiguous import
+section and then ordinary top-level declarations. A later import is a parser
+error, `imports must appear before other declarations`. The imports-only load
+pass diagnoses the first import in each separated late section before graph or
+producer construction; the full parser gives direct compiler input the same
+result. Consequently an invalid test source creates no variant, generated main,
+test binary, runtime process, accounting, retained output, or new persistent
+generation. The directory command retains its existing attributable final
+`FAIL\n`. Wrong-target files remain excluded before this rule and contribute no
+diagnostic. This ordering state is per source and never package, import,
+variant, action, artifact, publication, or persistence identity.
+
 After that eligibility boundary and the coordinator's required package-clause
 classification and production `@test` validation parses, the delegated loader
 performs selected-basename Go 1.26.5 simple-fold preflight before its graph