fix: use correct subagent flag instead of nonexistent agent attr

The checkpoint guard referenced `args.agent` which is never set — the
actual CLI flag is `--subagent`. The old check always evaluated to False,
making the condition equivalent to just `self.args.all`.

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

Author: aseembits93

codeflash/optimization/optimizer.py

@@ -604,7 +604,7 @@ def run(self) -> None:
                 return
 
             function_to_tests, _ = self.discover_tests(file_to_funcs_to_optimize)
-            if self.args.all and not getattr(self.args, "agent", False):
+            if self.args.all and not self.args.subagent:
                 self.functions_checkpoint = CodeflashRunCheckpoint(self.args.module_root)
 
             # GLOBAL RANKING: Rank all functions together before optimizing