test: add KUGETSU_TEMP_DIR export test

Add unit test to verify KUGETSU_TEMP_DIR is exported in cmd_delegate.
Also update SKILL.md to document KUGETSU_TEMP_DIR config option.

skills/kugetsu/tests/test-kugetsu-v2.sh

@@ -634,6 +634,15 @@ else
 fi
 echo ""
 
+# Test E7: KUGETSU_TEMP_DIR is exported in cmd_delegate
+echo "--- Test: KUGETSU_TEMP_DIR export in cmd_delegate ---"
+if grep -q "KUGETSU_TEMP_DIR" "$KUGETSU" && grep -q "export KUGETSU_TEMP_DIR" "$KUGETSU"; then
+    pass "KUGETSU_TEMP_DIR is exported to delegated agents"
+else
+    fail "KUGETSU_TEMP_DIR not found in cmd_delegate export"
+fi
+echo ""
+
 # Cleanup env files
 rm -rf ~/.kugetsu/env 2>/dev/null || true