Fix ActiveRecord with_tool/with_tools resetting messages mid-conversation

[ebeigarts]

When a tool dynamically registers new tools during execution (e.g., a ToolSearch tool that calls chat.with_tool to make discovered tools available), the ActiveRecord with_tool/with_tools methods were calling to_llm which reset all messages from the database. This inserted an extra empty assistant message between the tool_calls message and its tool result, violating the OpenAI API contract and causing a RubyLLM::BadRequestError.

An assistant message with 'tool_calls' must be followed by tool messages responding to each 'tool_call_id'. The following tool_call_ids did not have response messages: call_bcf3b9FOG3G3wxc2OW7Zg3CI (RubyLLM::BadRequestError)

The solution is to add a reset_messages parameter to to_llm so that with_tool/with_tools can initialize the chat object without disrupting the in-flight message sequence.

To reproduce the issue: https://gist.github.com/ebeigarts/dae372091c42756c3bdf1fa9e2d5f2ef

[ebeigarts]

Maybe it would be better to just use this instead?

  def with_tool(...)
    (@chat || to_llm).with_tool(...)
    self
  end

  def with_tools(...)
    (@chat || to_llm).with_tools(...)
    self
  end

[jayelkaake]

Ran into this issue as well.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.64%. Comparing base (5c59d9b) to head (e9cc082).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #689      +/-   ##
==========================================
+ Coverage   81.60%   81.64%   +0.03%     
==========================================
  Files         124      124              
  Lines        6079     6080       +1     
  Branches     1079     1080       +1     
==========================================
+ Hits         4961     4964       +3     
+ Misses        682      681       -1     
+ Partials      436      435       -1     

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