Fix coercion through schema unions and type references

[datduyng]

editorPosition is declared as EditorPosition | number. The input "1" can be coerced to 1, but union/type-reference validation discarded that result and left the original string for later validation.

This is an inconsistent experience because in https://github.com/microsoft/TypeAgent/blob/15ef5aa0362e3296bd9d6bd2f001fab704375d27/ts/packages/actionSchema/src/validate.ts

we explicitly allowed casting string to number but not at the stored value level.

> @action code splitEditor --parameters {"editorPosition":"1","direction":"down"}

Input:  editorPosition = "1" (string)
Schema: EditorPosition | number

Before:
  number branch -> 1 (number)
  stored value  -> "1" (string)
  output        -> Action parameter type mismatch editorPosition: value doesn't match any of the union type

After:
  number branch -> 1 (number)
  stored value  -> 1 (number)
  output        -> Split editor (1) down

The fix returns coerced values through union and type-reference wrappers so the parent object stores the declared type.

pr-2711-before-after.mp4