Fix missing logs when calling oneshot (#1446)

Fix missing logs when calling oneshot #1441 

Summary:

When calling oneshot (e.g., in gemma2_example.py), a sparse_logs folder
is created, but the log file inside is nearly empty. This is because the
logging setup in lifecycle.py and state.py uses loguru, but oneshot
itself didn’t configure loguru to write logs to a file. As a result,
logs were not being saved properly.

This PR fixes the issue by adding a log file configuration directly in
the oneshot init. This ensures loguru writes to the appropriate file by
default.

To clean up the nearly empty log file, I removed the two lines from
stage.py that were generating it. These messages appear to be redundant,
as similar info is already captured by loguru.

Currently, I set the log path defaults to sparse_logs. Maybe we can
consider making the log file path an optional input, allowing users to
disable file logging by passing None. Let me know what you guys think.

Test Plan:

Ran gemma2_example.py after the changes:
A proper log file was generated in sparse_logs
The original nearly empty log file was no longer created

Also ran make test and got the same results as the current main.

---------

Signed-off-by: Kelvin Cheng <kelvincheng216@gmail.com>
Co-authored-by: Kyle Sayers <kylesayrs@gmail.com>

Author: kelkelcheng

src/llmcompressor/entrypoints/oneshot.py

@@ -1,5 +1,8 @@
+import os
+from datetime import datetime
 from typing import Optional
 
+from loguru import logger
 from torch.utils.data import DataLoader
 from transformers import PreTrainedModel
 
@@ -82,6 +85,7 @@ class Oneshot:
 
     def __init__(
         self,
+        log_dir: Optional[str] = "sparse_logs",
         **kwargs,
     ):
         """
@@ -100,6 +104,15 @@ def __init__(
         :param output_dir: Path to save the output model after carrying out oneshot
 
         """
+        # Set up logging
+        if log_dir:
+            os.makedirs(log_dir, exist_ok=True)
+            date_str = datetime.now().strftime("%Y-%m-%d_%H-%M-%S")
+            logger.add(
+                f"{log_dir}/oneshot_{date_str}.log",
+                level="DEBUG",
+            )
+
         model_args, dataset_args, recipe_args, _, output_dir = parse_args(**kwargs)
 
         self.model_args = model_args

src/llmcompressor/modifiers/stage.py

@@ -67,7 +67,6 @@ def initialize(self, state: "State", **kwargs):
                 modifier.initialize(state, **kwargs)
             if accelerator:
                 accelerator.wait_for_everyone()
-        state.loggers.system.info(tag="stage", string="Modifiers initialized")
 
     def finalize(self, state: "State", **kwargs):
         """
@@ -88,7 +87,6 @@ def finalize(self, state: "State", **kwargs):
                 accelerator.wait_for_everyone()
 
         self.applied = True
-        state.loggers.system.info(tag="stage", string="Modifiers finalized")
 
     def update_event(self, state: "State", event: "Event", **kwargs):
         """