Add 32-bit platform testing to CI

[Copilot]

Adds CI job to detect 32-bit platform regressions (e.g., issue #47).

Changes

• New test-32bit job in .github/workflows/go.yml
  • Runs in i386/golang:1.23 Docker container on ubuntu-latest
  • Executes full build, vet, and test suite with race detection
  • Triggers on push/PR to main and master branches
  • Includes permissions: contents: read for least-privilege security

Checklist

• I have read the contribution guidelines.
• make test passes.
• make lint passes.
• New and changed code is covered by tests.
• Performance improvements include benchmarks.
• Changes match the documented (not just the implemented) behavior of Shopify.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Add 32-bit platform to CI</issue_title>
<issue_description>Add a CI step to build and test on a 32-bit platform. This will detect a regression in #47 or the introduction of similar bugs.

I believe this requires building and testing on a 32-bit Docker container.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add 32-bit platform to CI #49

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