Enhance agent command handling and logging

- Updated the `main.rs` to allow specifying a goal either directly or via a file, improving flexibility in agent command execution.
- Removed unused diagnostic logging functions and variables in `mod.rs` to streamline the code and reduce clutter.
- Deleted obsolete grammar test file `test_grammar.txt`.
- Added example configuration for MCP servers in `.mcp.json.example`.
- Introduced a comprehensive tutorial on building agentic agents in `tutorial_agentic.md`, covering setup, tool registration, and multi-agent collaboration.

Author: netdur

.mcp.json.example

@@ -0,0 +1,8 @@
+{
+  "mcpServers": {
+    "hugind": {
+      "command": "hugind",
+      "args": ["stdio"]
+    }
+  }
+}