[Bug] Inbuilt move_one_step tool called unexpectedly when only domain tool is registered

[nancysangani]

Environment

• mesa-llm: 0.3.0
• mesa: latest
• Python: 3.x
• Provider: groq/llama-3.1-8b-instant

Description
When an agent registers only a single domain-specific tool
(e.g. adopt_opinion), the executor sometimes calls an inbuilt
tool (move_one_step) instead — even when the prompt has nothing
to do with movement.

Minimal reproduction
Found while building an opinion spread POC model:
https://github.com/nancysangani/GSoC-learning-space/blob/main/models/opinion_spread/model.py

Agent 6, Step 2:

• Agent is prompted to decide whether to adopt a neighbor's opinion
• CoT reasoning concludes: "I will express continued support for Universal healthcare"
• Plan-Execution calls: move_one_step(direction="NorthEast")
• Result: agent physically moves on the grid instead of making an opinion decision

Root cause hypothesis
mesa-llm registers inbuilt tools (including move_one_step) globally
by default via ToolManager. When tool_choice="required" forces the
executor to call something, the LLM picks from all available tools —
including inbuilt ones the user never intended to expose for this task.

Suggested fix
Option A: Do not register inbuilt tools globally by default — require
explicit opt-in via tool_manager.register(move_one_step)
Option B: Add a tools_whitelist parameter to reasoning.plan() so
the user can restrict which tools the executor can pick from
Option C: Warn the user at agent init time which inbuilt tools are
auto-registered, so the behavior is not surprising