API Simplification

[BinaryMuse]

This issue serves as a high-level implementation plan and tracking issue for a suite of features designed to simplify the API. The largest shifts are #3, #5, and #6.

#	Item	Risk	Impact	Depends on
1	View component	Low	High	Nothing
2	Render-and-measure unification	Medium	High	Nothing
3	Unified view() method	Medium-High	Very high	2
4	impl_slot_children! elimination	—	—	Comes free with 3
5	Text model rethink (replace TextBlock)	Low-Med	High	4 (View)
6	simple_component! macro	Low	Moderate	3 (ideally)
7	#[component] attribute macro	High effort	High	3, 6
8	Effects / async in components	High	Moderate	3
9	Domain events	Medium	Moderate	3 (likely)