fix: Improve MCP server robustness and debugging

- Refactor  for more reliable project root detection, particularly when running within integrated environments like Cursor IDE. Includes deriving root from script path and avoiding fallback to '/'.
- Enhance error handling in :
    - Add detailed debug information (paths searched, CWD, etc.) to the error message when  is not found in the provided project root.
    - Improve clarity of error messages and potential solutions.
- Add verbose logging in  to trace session object content and the finally resolved project root path, aiding in debugging path-related issues.
- Add default values for  and  to the example  environment configuration.

.cursor/mcp.json

@@ -0,0 +1,20 @@
+{
+    "mcpServers": {
+        "taskmaster-ai": {
+            "command": "node",
+            "args": [
+                "./mcp-server/server.js"
+            ],
+            "env": {
+                "ANTHROPIC_API_KEY": "%ANTHROPIC_API_KEY%",
+                "PERPLEXITY_API_KEY": "%PERPLEXITY_API_KEY%",
+                "MODEL": "%MODEL%",
+                "PERPLEXITY_MODEL": "%PERPLEXITY_MODEL%",
+                "MAX_TOKENS": "%MAX_TOKENS%",
+                "TEMPERATURE": "%TEMPERATURE%",
+                "DEFAULT_SUBTASKS": 5,
+                "DEFAULT_PRIORITY": "medium"
+            }
+        }
+    }
+}