feat: add review_pending_changes tool and enforce absolute path security

- Add new review_pending_changes tool for comprehensive pre-commit reviews
- Implement filesystem sandboxing with MCP_PROJECT_ROOT
- Enforce absolute paths for all file/directory operations
- Add comprehensive git utilities for repository management
- Update all tools to use centralized path validation
- Add extensive test coverage for new features and security model
- Update documentation with new tool and path requirements
- Remove obsolete demo and guide files

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tools/think_deeper.py

@@ -27,7 +27,8 @@ class ThinkDeeperRequest(ToolRequest):
         description="Specific aspects to focus on (architecture, performance, security, etc.)",
     )
     files: Optional[List[str]] = Field(
-        None, description="Optional file paths or directories for additional context"
+        None,
+        description="Optional file paths or directories for additional context (must be absolute paths)",
     )
 
 
@@ -66,7 +67,7 @@ class ThinkDeeperTool(BaseTool):
                 "files": {
                     "type": "array",
                     "items": {"type": "string"},
-                    "description": "Optional file paths or directories for additional context",
+                    "description": "Optional file paths or directories for additional context (must be absolute paths)",
                 },
                 "temperature": {
                     "type": "number",