dynamic_fork sets deprecated dynamicForkJoinTasksParam — should use dynamicForkTasksParam

## Summary

`TaskRef#apply_dynamic_fork_fields` assigns the DSL's `dynamic_fork_tasks_param` option to the **deprecated** `dynamicForkJoinTasksParam` JSON field instead of the current `dynamicForkTasksParam` field. The server still accepts the deprecated field via a fallback path, so it currently works — but the fallback may be removed in a future server version.

Tested against: **Conductor OSS 3.32.0-rc.9**

## Root Cause

```ruby
# lib/conductor/workflow/dsl/task_ref.rb:171-174
def apply_dynamic_fork_fields(wf_task)
wf_task.dynamic_fork_join_tasks_param = @options[:dynamic_fork_tasks_param] # ← deprecated field
wf_task.dynamic_fork_tasks_input_param_name = @options[:dynamic_fork_tasks_input_param]
end
```

The `WorkflowTask` model has two distinct fields:
- `dynamic_fork_join_tasks_param` → JSON `"dynamicForkJoinTasksParam"` (deprecated)
- `dynamic_fork_tasks_param` → JSON `"dynamicForkTasksParam"` (current)

The option key `:dynamic_fork_tasks_param` correctly names the current field, but the assignment goes to the deprecated attribute.

## Server Behavior

`ForkJoinDynamicTaskMapper.java:156` reads `getDynamicForkTasksParam()` first; if null, falls back to `getDynamicForkJoinTasksParam()`. The deprecated fallback currently works, but is subject to removal.

## Fix

```ruby
def apply_dynamic_fork_fields(wf_task)
wf_task.dynamic_fork_tasks_param = @options[:dynamic_fork_tasks_param] # non-deprecated
wf_task.dynamic_fork_tasks_input_param_name = @options[:dynamic_fork_tasks_input_param]
end
```

Related: C# SDK [#159](https://github.com/conductor-oss/csharp-sdk/issues/159) — same pattern.

Start in lib/conductor/workflow/dsl/task_ref.rb at TaskRef#apply_dynamic_fork_fields and inspect the WorkflowTask attributes named in the issue. Compare the generated field with ForkJoinDynamicTaskMapper.java:156, then run the repository’s existing tests and verify the current dynamicForkTasksParam JSON field is populated without relying on the deprecated field.

Written by the indexing model from the issue text.