feat(nanoviews): rename $$children, $$slot and $$slots to a trailing $

[dangreen]

Effect attributes lost the $$ prefix in #188 and took a trailing $ instead — classList$, value$, ref$, autoFocus$. These three kept the old spelling:

-export function $$children<T extends Child, C extends unknown[] = Children>(render: Renderer<T, C>)
+export function children$<T extends Child, C extends unknown[] = Children>(render: Renderer<T, C>)

-export function $$slot<C, F extends (...args: any[]) => Slot<C, F>>(factory: F, content: C)
+export function slot$<C, F extends (...args: any[]) => Slot<C, F>>(factory: F, content: C)

-export function $$slots<T extends Child, D extends AnySlotDef[]>(slotDefs: [...D], render: RendererWithSlots<T, D>)
+export function slots$<T extends Child, D extends AnySlotDef[]>(slotDefs: [...D], render: RendererWithSlots<T, D>)

They are the names a component author writes most, so the inconsistency was in the most visible place.

Cost

None. The package is not published yet, so the old names go rather than turn into aliases, and the rename is free at every measured entry:

gzip	before	after
all publics	7419	7417
average usage	3790	3790

The average-usage entry names its imports, so $$children there became children$ too. One brotli pin moves down a step.

114 tests, lint and tsc --noEmit green.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.30%. Comparing base (024e812) to head (f32e54a).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #209      +/-   ##
==========================================
- Coverage   85.33%   85.30%   -0.04%     
==========================================
  Files         139      139              
  Lines        3143     3143              
  Branches      591      591              
==========================================
- Hits         2682     2681       -1     
  Misses        332      332              
- Partials      129      130       +1     

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