[blemale]

Closes #27.

Summary

• Adds Generators.optionalInts(Generator<Integer>), optionalLongs(Generator<Long>) and optionalDoubles(Generator<Double>). Each generates either an empty primitive optional or one wrapping a value from the given generator, and shrinks toward empty, like optional.
• forType / records now derive OptionalInt, OptionalLong and OptionalDouble (from integers(), longs(), doubles()), so record Stats(long count, OptionalLong max, OptionalDouble mean) derives without an override.

Review notes

These are new names rather than overloads of optional, as discussed in the issue. Because IntegerGenerator implements Generator<Integer>, an optional(IntegerGenerator) overload would be picked over the generic one, so existing calls like optional(integers().min(0).max(3)) would silently change from Optional<Integer> to OptionalInt, while optional(integers().filter(...)) would not.

Testing

• ConformanceTest.optional{Ints,Longs,Doubles}BoundsAndShrinking: for each type, values stay within the inner generator's bounds, an unconstrained draw shrinks to empty, and a present value shrinks to the inner generator's lower bound.
• GeneratorSmokeTest: draws one value of each type.
• DerivationTest.derivesPrimitiveOptionals: derives a record with all three.
• mvn verify passes locally (both backends, 100% coverage gate); spotless:check clean.

[blemale]

The test (java 25) failure looks flaky and unrelated to this PR. All tests pass in that job, only the JaCoCo check on hegel drops to 99%, while the java 22, macOS and Windows jobs pass the 100% gate on the same commit.

I couldn't reproduce it on Linux x86-64 with Temurin 25.0.4, the JDK the failing job used. One full mvn -B verify run and 10 more runs of the hegel module all reached 100% coverage. Script, run from the repository root:

git archive HEAD | docker run --rm -i --platform linux/amd64 -e CI=true \
  maven:3.9-eclipse-temurin-25 bash -c '
    mkdir /src && tar -x -C /src && cd /src
    apt-get -qq update && apt-get -qq install -y python3 >/dev/null
    mvn -B verify'

Could someone re-run the failed job?

[esauro]

It passed this time and it passed for me locally too several times