fix: improve shell compatibility and process cleanup

Preserve literal paths and arguments, use portable command options, validate startup configuration, and retain scripts when downloads fail.

Ensure task watchdogs and process groups are cleaned up across Bash versions, with compatibility and process lifecycle regression coverage.

test/back/qlServiceLogCommand.test.cjs

@@ -101,7 +101,7 @@ test('ql log follows the current Winston system log without PM2', () => {
   );
 
   assert.equal(result.status, 0, result.stderr);
-  assert.equal(result.stdout, `tail <-n> <0> <--retry> <-F> <${currentLog}>\n`);
+  assert.equal(result.stdout, `tail <-n> <0> <-F> <${currentLog}>\n`);
   assert.equal(fs.existsSync(path.join(testRoot, 'data/log/log')), false);
 });