fix: resolve all ruff linting errors (W293, F401, B904, UP007, UP045, E741, SIM102, SIM117, ARG)

Auto-fixed (whitespace, imports, type annotations):
- codebase_scraper.py: W293 blank lines with whitespace
- doc_scraper.py: W293 blank lines with whitespace
- parsers/extractors/__init__.py: W293
- parsers/extractors/base_parser.py: W293, UP007, UP045, F401

Manual fixes:
- enhancement_workflow.py: B904 raise without `from exc`, remove unused `os` import
- parsers/extractors/quality_scorer.py: E741 ambiguous var `l` → `line`
- parsers/extractors/rst_parser.py: SIM102 nested if → combined conditions (x2)
- pdf_scraper.py: F821 undefined `logger` → `print()` (consistent with file style)
- mcp/tools/workflow_tools.py: ARG001 unused `args` → `_args`
- tests/test_workflow_runner.py: ARG005 unused lambda args → `_a`/`_kw`, ARG001 `kwargs` → `_kwargs`
- tests/test_workflows_command.py: SIM117 nested with → combined with (x2)

All 1922 tests pass.

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

src/skill_seekers/cli/pdf_scraper.py

@@ -707,14 +707,14 @@ def main():
         # Note: Runs independently of workflow system (they complement each other)
         if getattr(args, "enhance_level", 0) > 0:
             # Traditional AI enhancement (API or LOCAL mode)
-            logger.info("\n" + "=" * 80)
-            logger.info("🤖 Traditional AI Enhancement")
-            logger.info("=" * 80)
+            print("\n" + "=" * 80)
+            print("🤖 Traditional AI Enhancement")
+            print("=" * 80)
             if workflow_executed:
-                logger.info(f"   Running after workflow: {workflow_name}")
-                logger.info("   (Workflow provides specialized analysis, enhancement provides general improvements)")
-            logger.info("   (Use --enhance-workflow for more control)")
-            logger.info("")
+                print(f"   Running after workflow: {workflow_name}")
+                print("   (Workflow provides specialized analysis, enhancement provides general improvements)")
+            print("   (Use --enhance-workflow for more control)")
+            print("")
             # Note: PDF scraper uses enhance_level instead of enhance/enhance_local
             # This is consistent with the new unified enhancement system