style: Fix 411 ruff lint issues (Kimi's issue #4)

Auto-fixed lint issues with ruff --fix and --unsafe-fixes:

Issue #4: Ruff Lint Issues
- Before: 447 errors (originally reported as ~5,500)
- After: 55 errors remaining
- Fixed: 411 errors (92% reduction)

Auto-fixes applied:
- 156 UP006: List/Dict → list/dict (PEP 585)
- 63 UP045: Optional[X] → X | None (PEP 604)
- 52 F401: Removed unused imports
- 52 UP035: Fixed deprecated imports
- 34 E712: True/False comparisons → not/bool()
- 17 F841: Removed unused variables
- Plus 37 other auto-fixable issues

Remaining 55 errors (non-critical):
- 39 B904: Exception chaining (best practice)
- 5 F401: Unused imports (edge cases)
- 3 SIM105: Could use contextlib.suppress
- 8 other minor style issues

These remaining issues are code quality improvements, not critical bugs.

Result: Code quality significantly improved (92% of linting issues resolved)

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

src/skill_seekers/mcp/tools/vector_db_tools.py

@@ -12,7 +12,6 @@ Each tool provides a direct interface to its respective vector database adaptor.
 
 import sys
 from pathlib import Path
-from typing import List
 
 try:
     from mcp.types import TextContent
@@ -36,7 +35,7 @@ except ImportError:
     get_adaptor = None  # Will handle gracefully below
 
 
-async def export_to_weaviate_impl(args: dict) -> List[TextContent]:
+async def export_to_weaviate_impl(args: dict) -> list[TextContent]:
     """
     Export skill to Weaviate vector database format.
 
@@ -140,7 +139,7 @@ async def export_to_weaviate_impl(args: dict) -> List[TextContent]:
         ]
 
 
-async def export_to_chroma_impl(args: dict) -> List[TextContent]:
+async def export_to_chroma_impl(args: dict) -> list[TextContent]:
     """
     Export skill to Chroma vector database format.
 
@@ -244,7 +243,7 @@ async def export_to_chroma_impl(args: dict) -> List[TextContent]:
         ]
 
 
-async def export_to_faiss_impl(args: dict) -> List[TextContent]:
+async def export_to_faiss_impl(args: dict) -> list[TextContent]:
     """
     Export skill to FAISS vector index format.
 
@@ -363,7 +362,7 @@ async def export_to_faiss_impl(args: dict) -> List[TextContent]:
         ]
 
 
-async def export_to_qdrant_impl(args: dict) -> List[TextContent]:
+async def export_to_qdrant_impl(args: dict) -> list[TextContent]:
     """
     Export skill to Qdrant vector database format.