Reimplement Form objects as Typed

Rename form objects to Typed (exact name is open for discussion).

Create coherent plan around:
- Type checking
- Validation
- Serialization

Change dependencies to implement the above.

No files, tests, or entry points are named. Start by locating the existing form objects and their dependency definitions, then map current type checking, validation, and serialization behavior; done requires an agreed name and a coherent implementation plan covering all three areas.

Written by the indexing model from the issue text.