feat!: port property tests to effect/unstable/arbitrary

[BleedingDev]

Effect-TS/effect#7254 | ScriptedAlchemy/effect-rstest#5

Why the change

Effect 4.0.0-rc.113 removed effect/testing/FastCheck, so effect-rstest@0.1.5 fails to import on current Effect, so this PR moves the property-test helpers to effect/unstable/arbitrary, as upstream @effect/vitest did.

Special things to note

• Breaking change (feat!): the fastCheck option is now arbitrary (Arbitrary.CheckOptions), and the effect peer range is now >=4.0.0-rc.113 <5.0.0.
• With the current release-please config, a breaking change on 0.x proposes 1.0.0. To ship 0.2.0 instead, add "bump-minor-pre-major": true or a Release-As: 0.2.0 footer when merging.
• The same port already landed in feat!: port prop to effect/unstable/arbitrary (effect rc.113+) ScriptedAlchemy/effect-rstest#5. We'd like to install it from npm instead of pkg.pr.new previews.

Change outline

Files changed:

  package.json            ~ effect peer >=4.0.0-rc.113, dev pin 4.0.0-rc.117
  pnpm-lock.yaml          - fast-check removed
  src/
    index.ts              ~ option types: fastCheck -> arbitrary
    internal/internal.ts  ~ FC.* -> Arbitrary.*
  test/ + typetest/       ~ updated to the new API, plus a test for a property that returns false
  README.md               ~ migration notes

How a property test runs now:

  it.prop(name, inputs, property, options)
    inputs (Schema | Arbitrary, as a tuple or a record)
-     Schema.toArbitrary(input)(FC)  ->  FC.tuple / FC.record
+     Arbitrary.schema(input)        ->  Arbitrary.all(...)
-   FC.assert(FC.asyncProperty(...), options.fastCheck)
+   runTest(ctx)(Arbitrary.checkEffect(arbitrary, property, options.arbitrary))
+     failure -> Effect.die(new Error(Arbitrary.formatCheckFailure(result)))

Failing properties still shrink. The test timeout now also interrupts generation and shrinking.

What changes for users:

- { fastCheck: { numRuns: 5, seed: 1001 } }
+ { arbitrary: { runs: 5, seed: 1001 } }

Test plan

• pnpm check, pnpm test (105 passed), pnpm build, pnpm test:types (TS 5.9 and 6.0)

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