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/arguments/unified.py

@@ -6,10 +6,9 @@ import and use these definitions.
 """
 
 import argparse
-from typing import Dict, Any
+from typing import Any
 
-
-UNIFIED_ARGUMENTS: Dict[str, Dict[str, Any]] = {
+UNIFIED_ARGUMENTS: dict[str, dict[str, Any]] = {
     "config": {
         "flags": ("--config", "-c"),
         "kwargs": {
@@ -43,7 +42,6 @@ UNIFIED_ARGUMENTS: Dict[str, Dict[str, Any]] = {
     },
 }
 
-
 def add_unified_arguments(parser: argparse.ArgumentParser) -> None:
     """Add all unified command arguments to a parser."""
     for arg_name, arg_def in UNIFIED_ARGUMENTS.items():