fix: address 7 security and reliability issues

- Prevent path traversal in gitignore template names (Critical)
- Fix TOCTOU races in file operations with try/except pattern (High)
- Add timeout to HuggingFace API requests (Medium)
- Add missing %x00 separator in changelog fallback format (Medium)
- Filter unsanitized kwargs before passing to OpenAI SDK (High)
- Use context managers for proper client cleanup in providers (High)
- Exit with non-zero code on commit engine failure (Low)

devgen/modules/gitignore_generator.py

@@ -1,3 +1,4 @@
+import re
 from pathlib import Path
 from typing import List
 
@@ -5,6 +6,9 @@ import requests
 
 from devgen.utils import configure_logger
 
+# Only allow safe characters in template names to prevent path traversal
+_TEMPLATE_NAME_RE = re.compile(r"^[a-zA-Z0-9._-]+$")
+
 
 class GitignoreGenerator:
     """Fetches and manages .gitignore templates from GitHub."""
@@ -41,6 +45,11 @@ class GitignoreGenerator:
         self, name: str, use_cache: bool = True, offline: bool = False
     ) -> str:
         """Fetches template content from cache or GitHub."""
+        if not _TEMPLATE_NAME_RE.match(name):
+            raise ValueError(
+                f"Invalid template name '{name}'. "
+                "Names must contain only alphanumeric characters, hyphens, dots, or underscores."
+            )
         cache_file = self.cache_dir / f"{name}.gitignore"
 
         if offline: