fix: Convert Continue-As-New suggestion reason symbol to int

[jasonligg]

What was changed

This PR proposes two changes each as their own commit:

• 3908113
  • Fixes WorkflowInstance#activate to convert bridge enum symbols to integers using ProtoUtils.enum_to_int instead of calling .to_i directly on suggest_continue_as_new_reasons.
  • Updates the integration test (HistoryInfoWorkflow) to also assert on suggest_continue_as_new_reasons.
  • Updates the CHANGELOG.md to move the existing changes under a release for 1.5.0. This was probably forgotten for the most recent release.
• 16361c6
  • Updates the proto code generator (proto_gen.rb) to preserve repeated enum field type information in generated RBS signatures (using a new _RepeatedEnumField interface).
  • Adds an internal _Activation RBS interface for WorkflowInstance#activate, replacing the previous untyped activation parameter so Steep can see the repeated enum reason types used by the workflow instance code.
  • Regenerates RBS signatures.
  • Adds unit tests for both the proto gen normalization and the workflow instance continue-as-new reason handling.

Why?

The first commit addresses the actual problem encountered during workflow execution. When a workflow's history grows large enough for Temporal to suggest continue-as-new, the bridge returns suggest_continue_as_new_reasons as an array of protobuf enum symbols (e.g., :SUGGEST_CONTINUE_AS_NEW_REASON_TOO_MANY_HISTORY_EVENTS). The existing code called .to_i on these symbols, which raises undefined method 'to_i' for an instance of Symbol. This caused workflow tasks to fail repeatedly, leaving workflows permanently stuck.

The second commit is a bit out-of-scope but I was thinking about how this could be avoided in the future. I understand that there are parts of the SDK that are intentionally kept wide or even untyped so this change may not be welcome. I'm not super familiar with Steep as I use Sorbet a lot at work so I get the gist (footguns 😅) of adding types to an untyped language like Ruby or JS/TS.

💡 I'm fine with reverting that commit if it isn't appropriate!

Checklist

1. Closes [Bug] Symbol Conversion on suggestContinueAsNew event. #463

2. How was this tested:

   • Added a unit test (WorkflowInstanceTest#test_continue_as_new_suggestion_reasons_are_visible_as_workflow_enum_ints) that exercises the activation path with symbol enum reasons.
   • Added a unit test for the proto gen RBS normalization.
   • Updated the existing test_history_info integration test to verify suggest_continue_as_new_reasons is returned correctly.

3. Any docs updates needed?

   • No

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