Fix flaky acts_as_model specs caused by RubyLLM.logger spec leaving config nil

[cgmoore120]

Problem

The acts_as_model "model registry integration" specs (loads models from database when configured, finds models from database) fail intermittently under the parallel test queue (bin/rspec-queue), with errors like:

Failure/Error: expect(models.all.map(&:id)).to include('test-model')

The failures are order-dependent: they only appear when certain specs land in the same worker, so they surface non-deterministically depending on how test-queue distributes examples (more likely on slower Ruby versions).

Root cause

The RubyLLM.logger spec resets the global config/logger in its after hook by setting them to nil instead of restoring the originals:

after do
  described_class.instance_variable_set(:@config, nil)
  described_class.instance_variable_set(:@logger, nil)
end

Once @config is left nil, the next access lazily rebuilds a fresh Configuration. But config.model_registry_source is only ever set once — in RubyLLM::ActiveRecord::ActsAs.included at load time — so the rebuilt config no longer has it. Any later spec in the same worker that relies on the database-backed model registry (Models#load_models reads config.model_registry_source) then silently falls back to the JSON registry and fails to find the test records.

This reproduces deterministically by running the two specs in order:

rspec spec/ruby_llm_spec.rb spec/ruby_llm/active_record/acts_as_model_spec.rb --order defined
# => acts_as_model registry integration: 2 failures

Fix

Use an around hook that saves and restores the original @config/@logger, so the logger spec leaves global state untouched. After the fix the same ordered run passes (22 examples, 0 failures), and ruby_llm_spec itself stays green.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.45%. Comparing base (44f3cc0) to head (42bbd3f).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #815      +/-   ##
==========================================
- Coverage   81.47%   81.45%   -0.03%     
==========================================
  Files         165      165              
  Lines        7402     7402              
  Branches     1233     1233              
==========================================
- Hits         6031     6029       -2     
- Misses        874      875       +1     
- Partials      497      498       +1     

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