Use output_dir for saving all evaluation images

Update eval_dataset.py to save all comparison images to the
configured output_dir instead of the current directory. This provides
better organization and allows users to specify where outputs should be
saved.

Changes:
- Add os import at top level
- Create output_dir at start of run_evaluation()
- Save all comparison images to output_dir
- Remove duplicate os imports
- Update init_rtc_processor() docstring to be more concise

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Alexander Soare <alexander.soare159@gmail.com>
Co-Authored-By: Claude <noreply@anthropic.com>

src/lerobot/policies/smolvla/modeling_smolvla.py

@@ -249,12 +249,8 @@ class SmolVLAPolicy(PreTrainedPolicy):
             ACTION: deque(maxlen=self.config.n_action_steps),
         }
 
-    def init_rtc_processor(self, verbose: bool = False):
-        """Initialize RTC processor with optional verbose logging.
-
-        Args:
-            verbose: Enable verbose debug logging in RTCProcessor (currently unused)
-        """
+    def init_rtc_processor(self):
+        """Initialize RTC processor if RTC is enabled in config."""
         self.rtc_processor = None
 
         if self.config.rtc_config is not None and self.config.rtc_config.enabled: