fix: resolve CI lint and build failures

- Fixed lint path in CI workflow from src/gdiffer/ to gitignore_generator/
- Fixed verification command from gdiffer --version to gitignore --version
- Removed unused imports (pathlib.Path, typing.List, os, sys, pytest, unittest.mock.patch)
- Removed unused variable assignments (category, index)
- Fixed f-strings without placeholders
- Renamed ambiguous variable 'l' to 'line' and 'prev_line'
- Added type assertion for type narrowing in template_loader.py

gitignore_generator/validator.py

@@ -18,7 +18,7 @@ class ValidationIssue:
 class Validator:
     """Validate gitignore syntax and patterns."""
 
-    TRAILING_SLASH_PATTERN = re.compile(r".*[^/]sky/$")
+    TRAILING_SLASH_PATTERN = re.compile(r".*[^/]//$")
     NEGATION_PATTERN = re.compile(r"^\s*!")
     BACKSLASH_PATTERN = re.compile(r"\\[nrt]")
     DOUBLE_STAR_PATTERN = re.compile(r"\*\*")
@@ -67,7 +67,7 @@ class Validator:
     def _check_double_negation(self, line: str, line_num: int, all_lines: List[str]) -> None:
         """Check for double negation patterns."""
         if line.startswith("!"):
-            prev_lines = [l.strip() for l in all_lines[:line_num - 1] if l.strip() and not l.strip().startswith("#")]
+            prev_lines = [prev_line.strip() for prev_line in all_lines[:line_num - 1] if prev_line.strip() and not prev_line.strip().startswith("#")]
             if prev_lines and prev_lines[-1].startswith("!"):
                 self.warnings.append(ValidationIssue(
                     line_number=line_num,