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/source_detector.py

@@ -7,13 +7,12 @@ local directory, PDF file, or config file based on patterns.
 import os
 import re
 from dataclasses import dataclass
-from typing import Dict, Any, Optional
+from typing import Any
 from urllib.parse import urlparse
 import logging
 
 logger = logging.getLogger(__name__)
 
-
 @dataclass
 class SourceInfo:
     """Information about a detected source.
@@ -25,11 +24,10 @@ class SourceInfo:
         raw_input: Original user input
     """
     type: str
-    parsed: Dict[str, Any]
+    parsed: dict[str, Any]
     suggested_name: str
     raw_input: str
 
-
 class SourceDetector:
     """Detects source type from user input and extracts relevant information."""
 
@@ -124,7 +122,7 @@ class SourceDetector:
         )
 
     @classmethod
-    def _detect_github(cls, source: str) -> Optional[SourceInfo]:
+    def _detect_github(cls, source: str) -> SourceInfo | None:
         """Detect GitHub repository source.
 
         Supports patterns: