Source group env.sh inside test runner container

The group's env.sh (setting TEST_PY_* flags) was only sourced on
the host. The Docker test runner container didn't see these values,
so env-isolated.bash defaults took over (all tests disabled).

Now source group env.sh before env-isolated.bash inside the container
so group-specific settings are preserved.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

test/infra/control/run-tests-isolated.bash

@@ -319,7 +319,17 @@ docker run \
         [ -n \"${MYSQL_BINLOG_BIN}\" ] && ln -sf \"${MYSQL_BINLOG_BIN}\" \"${WORKSPACE}/test-scripts/deps/mysqlbinlog\"
         [ -n \"${BINLOG_READER_BIN}\" ] && ln -sf \"${BINLOG_READER_BIN}\" \"${WORKSPACE}/test-scripts/deps/test_binlog_reader-t\"
 
-        # Source the local isolated environment
+        # Source group environment first (sets TEST_PY_* flags etc.)
+        if [ -n \"${TAP_GROUP}\" ]; then
+            BASE_GROUP=\$(echo \"${TAP_GROUP}\" | sed -E 's/[-_]g[0-9]+.*//')
+            if [ -f \"${WORKSPACE}/test/tap/groups/${TAP_GROUP}/env.sh\" ]; then
+                source \"${WORKSPACE}/test/tap/groups/${TAP_GROUP}/env.sh\"
+            elif [ -f \"${WORKSPACE}/test/tap/groups/\${BASE_GROUP}/env.sh\" ]; then
+                source \"${WORKSPACE}/test/tap/groups/\${BASE_GROUP}/env.sh\"
+            fi
+        fi
+
+        # Source the local isolated environment (defaults for unset vars)
         source ${SCRIPT_DIR}/env-isolated.bash
 
         # Dump ProxySQL configuration before running tests