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/codebase_scraper.py

@@ -444,7 +444,7 @@ def extract_markdown_structure(content: str) -> dict[str, Any]:
 def extract_rst_structure(content: str) -> dict[str, Any]:
     """
     Extract structure from ReStructuredText (RST) content.
-    
+
     Uses the enhanced unified RST parser for comprehensive extraction.
 
     RST uses underline-style headers:
@@ -474,13 +474,13 @@ def extract_rst_structure(content: str) -> dict[str, Any]:
     # Use the enhanced unified RST parser
     try:
         from skill_seekers.cli.parsers.extractors import RstParser
-        
+
         parser = RstParser()
         result = parser.parse_string(content, "<string>")
-        
+
         if result.success and result.document:
             doc = result.document
-            
+
             # Convert to legacy structure format for backward compatibility
             structure = {
                 "title": doc.title,
@@ -531,7 +531,7 @@ def extract_rst_structure(content: str) -> dict[str, Any]:
     except Exception as e:
         # Fall back to basic extraction if unified parser fails
         logger.warning(f"Enhanced RST parser failed: {e}, using basic parser")
-    
+
     # Legacy basic extraction (fallback)
     import re