fix: Resolve all linting errors from ruff

Fix 145 linting errors across CLI refactor code:

Type annotation modernization (Python 3.9+):
- Replace typing.Dict with dict
- Replace typing.List with list
- Replace typing.Set with set
- Replace Optional[X] with X | None

Code quality improvements:
- Remove trailing whitespace (W291)
- Remove whitespace from blank lines (W293)
- Remove unused imports (F401)
- Use dictionary lookup instead of if-elif chains (SIM116)
- Combine nested if statements (SIM102)

Files fixed (45 files):
- src/skill_seekers/cli/arguments/*.py (10 files)
- src/skill_seekers/cli/parsers/*.py (24 files)
- src/skill_seekers/cli/presets/*.py (4 files)
- src/skill_seekers/cli/create_command.py
- src/skill_seekers/cli/source_detector.py
- src/skill_seekers/cli/github_scraper.py
- tests/test_*.py (5 test files)

All files now pass ruff linting checks.

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

src/skill_seekers/cli/parsers/scrape_parser.py

@@ -7,7 +7,6 @@ consistency with the standalone doc_scraper module.
 from .base import SubcommandParser
 from skill_seekers.cli.arguments.scrape import add_scrape_arguments
 
-
 class ScrapeParser(SubcommandParser):
     """Parser for scrape subcommand."""
 
@@ -25,7 +24,7 @@ class ScrapeParser(SubcommandParser):
 
     def add_arguments(self, parser):
         """Add scrape-specific arguments.
-        
+
         Uses shared argument definitions to ensure consistency
         with doc_scraper.py (standalone scraper).
         """