ci(e2e): wire just e2e recipe to existing tests/e2e.sh

Adds the missing `just e2e` Justfile recipe that invokes `bash tests/e2e.sh`,
completing the Phase 5 CI wiring for wokelang.

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

Author: hyperpolymath

Justfile

@@ -9,6 +9,10 @@ build:
 test:
     cargo test
 
+# End-to-end structural validation
+e2e:
+    bash tests/e2e.sh
+
 # Format code
 format:
     cargo fmt