<CLASS DOES NOT EXIST>%Close...
is typical if try to access resultset or just delete rset  after leaving namespace %SYS.
Just reproduced it.

%SYS>w !,rset.%Next(),?5,rset.%Get("Directory"),!?30,rset.%Get("Size"),?40,rset.%Get("MaxSize")
 1    c:\intersystems\iris\mgr\enslib\
                              163       Unbegrenzt
%SYS>ZN "USER" 
USER>k rset
<CLASS DOES NOT EXIST>%CloseCursor+3^%SQL.ClassQueryResultSet.1 *SYS.Database
USER>

#1 there is no "SELECT LAST_SERIAL()" 

#2 depending what your expectation on LAST is I see 2 possible workarounds
#2A LAST = max:    "SELECT MAX(test_id) FROM test
#2B LAST = latest: "SELECT test_id, MAX(ID) FROM test GROUP BY  2"

#2B is based on the fact that you always have an  auto-incremented ID and it's a shortcut of
"SELECT test_id  FROM test where id = (SELECT max(ID) from junior.test)"
or
"SELECT TOP 1 test_id FROM test WHERE ID < 999999999999999999 ORDER BY ID DESC

the second line of the error msg tells you that SQLserver raised error 102

This error occurs when Adaptive Server detects a syntax error in a Transact-SQL® command or query. This error can occur when: A keyword is misspelled. ... You used a variable for a database name and your query contains a parser errorerror 102 is raised because the batch was never executed.
from:
http://infocenter.sybase.com/help/index.jsp?topic=/com.sybase.infocenter.dc00729.1500/html/errMessageAdvRes/CHDGFCCJ.htm

suggestion: Check the SQL-name of the generated class samples.people

Developing in the production environment is "high-risk extra class".
This doesn't exclude to do development on the production SERVER (e.g by lack of HW)
The most simple option is to have 3 namespaces in parallel. PRODUCTION (aka WORK), TEST, DEVELOPMENT.
A better variant is to have a 2nd instance on the same SERVER machine for  TEST & DEVELOPMENT.
Git doesn't care which Instance you use.
ZMP is not availaible in Caché.
Docker is theoretically possible but quite an effort as you need to build your own image especially for a WIN environment and get the appropriate license for it.