fix: Fix list comprehension variable names (NameError in CI)

Fixed incorrect variable names in list comprehensions that were causing
NameError in CI (Python 3.11/3.12):

Critical fixes:
- tests/test_markdown_parsing.py: 'l' → 'link' in list comprehension
- src/skill_seekers/cli/pdf_extractor_poc.py: 'l' → 'line' (2 occurrences)

Additional auto-lint fixes:
- Removed unused imports in llms_txt_downloader.py, llms_txt_parser.py
- Fixed comparison operators in config files
- Fixed list comprehension in other files

All tests now pass in CI.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

tests/test_bootstrap_skill.py

@@ -51,7 +51,7 @@ class TestBootstrapSkillScript:
         assert "description:" in content, "Header must have description"
 
     @pytest.mark.slow
-    def test_bootstrap_script_runs(self, project_root, tmp_path):
+    def test_bootstrap_script_runs(self, project_root, _tmp_path):
         """Test that bootstrap script runs successfully.
 
         Note: This test is slow as it runs full codebase analysis.