RBS: Narrow type signatures for props parameters

[justin808]

Summary

Several RBS type signatures currently use untyped for props parameters, but could be more precise.

Current Signatures

# In sig/react_on_rails/helper.rbs
def react_component: (
  String component_name,
  ?Hash[Symbol, untyped] options
) ?{ () -> untyped } -> safe_buffer

# In sig/react_on_rails/controller.rbs
def redux_store: (
  String store_name,
  ?props: untyped,
  ?immediate_hydration: bool
) -> void

Proposed Improvement

?props: (Hash[Symbol, untyped] | String)

Benefits

• More precise type checking
• Still accepts both common formats (Hash or JSON string)
• Better IDE support and autocomplete
• Catches type errors earlier

Related

Follow-up to PR #1945 - post-merge code review feedback

References

• lib/react_on_rails/helper.rb - props can be Hash or String
• lib/react_on_rails/controller.rb - similar pattern