feat(dsl): add VCR infrastructure for DSL functional tests

[mathiusj]

TL;DR

Part of: #570

Added VCR support for DSL workflow tests to enable reliable HTTP request recording and playback.

What changed?

• Enhanced the in_sandbox method in FunctionalTest to wrap execution in VCR cassettes
• Added configuration for RubyLLM to work with VCR during tests
• Created a new test case "VCR infrastructure works for DSL chat workflows" to verify functionality
• Added a VCR cassette file with a mock response about Lake Baikal
• Created a simple test workflow file vcr_test.rb that makes an LLM API call

How to test?

1. Run the new test: OPENAI_API_KEY=api-key-here RECORD_VCR=true bundle exec ruby -Itest test/dsl/functional/roast_dsl_examples_test.rb
2. Verify that tests pass without real API calls when using the recorded cassettes

Why make this change?

This change improves test reliability by eliminating dependencies on external API services during testing. By recording API interactions once and playing them back during subsequent test runs, we can:

• Make tests faster and more deterministic
• Avoid hitting rate limits or incurring costs from real API calls
• Test without requiring real API credentials
• Ensure consistent test behavior regardless of network conditions

[mathiusj]

• feat(dsl): add VCR infrastructure for DSL functional tests #655 👈 (View in Graphite)
• main

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[mathiusj]

@juniper-shopify updated approach to add VCR support for the functional tests. I can iterate on this a bit more if this looks right to you 🙏