`FrameworkProcessor._package_code` fails on Windows with `PermissionError` (WinError 32) when deleting temp tar.gz

**PySDK Version**
- [ ] PySDK V2 (2.x)
- [x] PySDK V3 (3.x)

**Describe the bug**

On Windows, calling `FrameworkProcessor.run()` with a local `source_dir` fails during code packaging with:

```
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\...\\AppData\\Local\\Temp\\tmpXXXX.tar.gz'
```

The failure occurs in `FrameworkProcessor._package_code()` at `os.unlink(tmp.name)` ([`sagemaker-core/src/sagemaker/core/processing.py`](https://github.com/aws/sagemaker-python-sdk/blob/master/sagemaker-core/src/sagemaker/core/processing.py) ~L1159–L1182).

The method creates a temp file with `tempfile.NamedTemporaryFile(..., delete=False)` and calls `os.unlink(tmp.name)` **inside** the `with` block, while the `NamedTemporaryFile` handle is still open. On Windows, a file cannot be deleted while any handle remains open; on Linux/macOS this pattern often succeeds.

**To reproduce**

1. Use Windows (tested on Windows 11).
2. Install PySDK V3, e.g. `pip install sagemaker-core` (tested with `sagemaker-core==2.11.0`).
3. Save and run the script below (no AWS credentials required; S3 upload is mocked):

```python
"""Minimal repro for FrameworkProcessor._package_code WinError 32 on Windows."""

import os
import sys
from unittest.mock import patch

if sys.platform != "win32":
print("Skip: this bug only reproduces on Windows.")
sys.exit(0)

from sagemaker.core.helper.session_helper import Session
from sagemaker.core.processing import FrameworkProcessor

SOURCE_DIR = "minimal_src"
os.makedirs(SOURCE_DIR, exist_ok=True)
with open(os.path.join(SOURCE_DIR, "script.py"), "w", encoding="utf-8") as f:
f.write("print('hello')\n")

sess = Session()
processor = FrameworkProcessor(
image_uri="123456789012.dkr.ecr.us-east-1.amazonaws.com/pytorch-training:1.0.0-cpu-py3",
role="arn:aws:iam::123456789012:role/SageMakerExecutionRole",
instance_type="ml.m5.large",
instance_count=1,
sagemaker_session=sess,
)

with patch("sagemaker.core.s3.S3Uploader.upload_string_as_file_body"):
processor._package_code(
entry_point="script.py",
source_dir=SOURCE_DIR,
requirements=None,
job_name="test-job",
kms_key=None,
)
```

4. Observe `PermissionError: [WinError 32]`.

**Real-world usage** (also fails before the processing job is created):

```python
from sagemaker.core.helper.session_helper import Session
from sagemaker.core.image_uris import get_training_image_uri
from sagemaker.core.processing import FrameworkProcessor

sess = Session()
processor = FrameworkProcessor(
image_uri=get_training_image_uri(
region=sess.boto_region_name,
framework="pytorch",
instance_type="ml.m5.large",
),
role="",
instance_type="ml.m5.large",
instance_count=1,
)

processor.run(
code="script.py", # script to execute
source_dir="src", # local directory
job_name="test-job",
wait=False,
)
```

**Expected behavior**

Code packaging completes successfully on Windows: the temporary `sourcedir.tar.gz` is removed after upload (or left for the OS to clean up), and `FrameworkProcessor.run()` proceeds to create the processing job.

**Screenshots or logs**

```
PermissionError: [WinError 32] The process cannot access the file because it is being used by another process:
'C:\\Users\\LORENZ~1\\AppData\\Local\\Temp\\tmp6qp3s0lg.tar.gz'
```

Traceback (abbreviated):

```
File ".../sagemaker/core/processing.py", line 1231, in run
s3_runproc_sh, inputs, job_name = self._pack_and_upload_code(...)
File ".../sagemaker/core/processing.py", line 1270, in _pack_and_upload_code
s3_payload = self._package_code(...)
File ".../sagemaker/core/processing.py", line 1182, in _package_code
os.unlink(tmp.name)
PermissionError: [WinError 32] ...
```

**System information**

- **SageMaker Python SDK version**: `sagemaker-core==2.11.0` (V3 imports: `sagemaker.core.*`)
- **Framework name (eg. PyTorch) or algorithm (eg. KMeans)**: PyTorch (`FrameworkProcessor` with PyTorch training image URI)
- **Framework version**: default from `get_training_image_uri` (py312 image selected automatically)
- **Python version**: 3.14.4
- **CPU or GPU**: CPU (local client); instance type `ml.m5.large` for the job definition
- **Custom Docker image (Y/N)**: N

**Additional context**

**Suggested fix:** Close the temp file before `unlink`, or use `tempfile.mkstemp` and avoid holding an open handle during deletion. For example:

```python
fd, tmp_path = tempfile.mkstemp(suffix=".tar.gz")
os.close(fd)
try:
with tarfile.open(tmp_path, "w:gz") as tar:
...
with open(tmp_path, "rb") as f:
body = f.read()
s3.S3Uploader.upload_string_as_file_body(body=body, ...)
return s3_uri
finally:
if os.path.exists(tmp_path):
os.unlink(tmp_path)
```

Alternatively, move `os.unlink(tmp.name)` **outside** the `NamedTemporaryFile` context manager (after the `with` block exits and the handle is closed).

Read sagemaker-core/src/sagemaker/core/processing.py, especially FrameworkProcessor._package_code() around the temporary archive creation and deletion. Run the supplied Windows reproduction with the S3 upload mocked, then verify that packaging removes or leaves the archive safely and FrameworkProcessor.run() proceeds without PermissionError.

Written by the indexing model from the issue text.