Introduce Natural Dialog forms system

[shah]

Create a Natural HTML dialog/forms runtime that is backed by Zod v4 schemas, leverages the native <dialog>/<form> contracts, and mirrors the design-system infrastructure for CSS/JS/UA dependency management.

Deliverables:

• authoring the fluent createDialog() builder, wiring helper renderers (inputField, selectField, etc.), and adding a focused test suite (dialog_test.ts) that validates both primitives and a full dialog render by comparing to golden HTML strings.
• Generalized factory that prepares middleware for all the SSE endpoints and allow full interactivity.
• Generalized factory that prepares diagnostics middleware and UI for easier testing.