[Epic] Enhance Type coercion

### Is your feature request related to a problem or challenge?

- [ ] #5928
- [x] #5931
- [x] #5933
- [ ] #6261
- [ ] feat: requestType (we can request type for child output, and build a more rigorous type system )

### Describe the solution you'd like

_No response_

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

This is an epic tracking child issues #5928, #5931, #5933, and #6261, plus a proposed requestType item; no files, tests, or entry points are named. Start by reviewing those child issues and the current type-coercion design, then determine the remaining scope and acceptance criteria before taking on a specific item.

Written by the indexing model from the issue text.