fix: Add TextContent fallback class for test compatibility

- Replace TextContent = None with proper fallback class in all MCP tool modules
- Fixes TypeError when MCP library is not fully initialized in test environment
- Ensures all 700 tests pass (was 699 passing, 1 failing)
- Affected files:
  * packaging_tools.py
  * config_tools.py
  * scraping_tools.py
  * source_tools.py
  * splitting_tools.py

The fallback class maintains the same interface as mcp.types.TextContent,
allowing tests to run successfully even when the MCP library import fails.

Test results: ✅ 700 passed, 157 skipped, 2 warnings

src/skill_seekers/mcp/tools/source_tools.py

@@ -20,7 +20,12 @@ try:
     from mcp.types import TextContent
     MCP_AVAILABLE = True
 except ImportError:
-    TextContent = None
+    # Graceful degradation: Create a simple fallback class for testing
+    class TextContent:
+        """Fallback TextContent for when MCP is not installed"""
+        def __init__(self, type: str, text: str):
+            self.type = type
+            self.text = text
     MCP_AVAILABLE = False
 
 import httpx