Improve allocation benchmark error handling for unmapped Ruby versions

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What are you trying to accomplish?

The assert_allocations helper fails silently with confusing error messages when a Ruby version isn't mapped in allocation expectations. This change makes the error explicit and actionable.

Before:

# Error: comparison of NilClass with Integer failed
assert_equal count, total, "..."  # count is nil for unmapped version

After:

# Error: No allocation count mapped for Ruby version 3.5. Available versions: 3.2, 3.3, 3.4. Actual allocations: 6

The improved error provides all information needed to add the new version mapping immediately.

Screenshots

N/A - test infrastructure change only

Integration

List the issues that this change affects.

Closes # (issue number not provided in problem statement)

Risk Assessment

• Low risk the change is small, highly observable, and easily rolled back.
• Medium risk changes that are isolated, reduced in scope or could impact few users. The change will not impact library availability.
• High risk changes are those that could impact customers and SLOs, low or no test coverage, low observability, or slow to rollback.

What approach did you choose and why?

Added nil check in assert_allocations_helper.rb that raises early with diagnostic information: unmapped version, available versions, and measured allocations. This makes adding new Ruby version support self-documenting.

Verified all existing Ruby 3.4 allocation counts are correct (tests pass on Ruby 3.4.7 and 3.3).

Anything you want to highlight for special attention from reviewers?

The change only adds error handling. No allocation counts were modified—all Ruby 3.4 values were already correct.

Accessibility

N/A - test infrastructure change only

Merge checklist

• Added/updated tests
• Added/updated documentation
• Added/updated previews (Lookbook)
• Tested in Chrome
• Tested in Firefox
• Tested in Safari
• Tested in Edge

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Original prompt

Fix the failing performance benchmark tests by ensuring that the allocation count expectations match Ruby 3.4.x (current CI version). Specifically:

1. Update all calls to assert_allocations in these files:

   • test/performance/bench_classify.rb
   • test/performance/bench_octicons.rb
   • test/performance/bench_utilities.rb

   Add or correct the value for the key "3.4" in their allocation expectation hash arguments so that the tests reflect current allocations. Run the benchmarks as needed to obtain the correct allocation counts for Ruby 3.4.x on this codebase.

2. (Optional but recommended): In test/test_helpers/assert_allocations_helper.rb, make the assertion logic friendlier for future Ruby versions by raising a meaningful error if the version is not mapped.

3. Do not alter unrelated code. The goal is only to make the allocation benchmarks robust against Ruby version changes and get CI passing.

This pull request was created as a result of the following prompt from Copilot chat.

Fix the failing performance benchmark tests by ensuring that the allocation count expectations match Ruby 3.4.x (current CI version). Specifically:

1. Update all calls to assert_allocations in these files:

   • test/performance/bench_classify.rb
   • test/performance/bench_octicons.rb
   • test/performance/bench_utilities.rb

   Add or correct the value for the key "3.4" in their allocation expectation hash arguments so that the tests reflect current allocations. Run the benchmarks as needed to obtain the correct allocation counts for Ruby 3.4.x on this codebase.

2. (Optional but recommended): In test/test_helpers/assert_allocations_helper.rb, make the assertion logic friendlier for future Ruby versions by raising a meaningful error if the version is not mapped.

3. Do not alter unrelated code. The goal is only to make the allocation benchmarks robust against Ruby version changes and get CI passing.

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Latest commit: ba33153

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