feat(nanoviews): rename the truthy and falsy narrowing types

[dangreen]

Four types in nanoviews narrow a value by whether it is truthy, and if_ hands two of them to its branches:

export function if_<T>($value: T) {
  return (
    then_: (value: TruthySignalish<T>) => Child,
    else_?: (value: FalsySignalish<T>) => Child
  ) => …
}

Their names were wrong in two different ways.

TruthyValueOrSignal and FalsyValueOrSignal were named after ValueOrAccessor, which became Signalish in #210 — so they were left pointing at a union that no longer exists.

TruthySignal and FalsySignal were never about signals: like their siblings they test Accessor, and answer never for anything that is not one.

-export type TruthySignal<T> = T extends Accessor<infer U>
+export type TruthyAccessor<T> = T extends Accessor<infer U>
   ? U extends FalsyValue
     ? never
     : T
   : never

-export type TruthyValueOrSignal<T> = T extends Accessor<infer U>
+export type TruthySignalish<T> = T extends Accessor<infer U>
   ? U extends FalsyValue
     ? never
     : T
   : T extends FalsyValue
     ? never
     : T

The suffix now carries the only thing that separates the two pairs: -Accessor requires an accessor and gives never to anything else, -Signalish also takes a plain value. That is the same opposition AccessorValue and SignalishValue already carry.

No aliases: the package is not published yet. TruthyAccessor and FalsyAccessor have no consumer anywhere in the monorepo — they could be deleted instead of renamed, which is a separate call to make.

Types only: every bundle is byte-identical and no pin moves. 114 tests, lint and tsc --noEmit green.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 85.33%. Comparing base (c42723a) to head (ae8ecd9).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #211   +/-   ##
=======================================
  Coverage   85.33%   85.33%           
=======================================
  Files         139      139           
  Lines        3143     3143           
  Branches      591      591           
=======================================
  Hits         2682     2682           
  Misses        332      332           
  Partials      129      129           

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