fix(ack): align numeric validation across platforms

[kauandotnet]

Summary

• Normalize losslessly representable JSON numeric inputs consistently across Dart VM and JavaScript, including SchemaType inference and safe-integer boundary handling.
• Make exported deep numeric equality and hashing platform-stable while retaining the dedicated Draft 7 uniqueItems behavior that landed in feat(generator): add AckInfer and AckModel generation #133.
• Document numeric normalization and anyOf branch ordering, and add a focused Chrome regression gate.

Context

The VM preserves an int/double representation boundary that JavaScript does not. Strict runtime-type checks therefore made mathematically equivalent JSON numbers validate differently across platforms. JSON Schema defines integers by value, so this change normalizes numeric values only when conversion is lossless.

#133 independently fixed Draft 7 uniqueItems equality. This branch now incorporates current main and preserves that implementation instead of replacing it.

Behavior changes

• Ack.integer() accepts finite numbers with no fractional part and returns an int when conversion is lossless.
• Ack.double() accepts exactly representable numeric inputs and returns a double.
• Integral inputs can match both schemas in Ack.anyOf; the first successful branch determines the runtime representation.
• Ack.number() continues to preserve the input's numeric representation.
• Ack.integer().safe() rejects values outside JavaScript's portable integer range without overflowing on the native minimum integer.

No public API signatures or generated JSON Schema shapes change.

Verification

• fvm dart run melos run ci --no-select — passed (strict analysis; root, Dart, and Flutter tests)
• Focused numeric, collection, and uniqueItems tests on Chrome — passed; one native-only precision case skipped as intended on JavaScript
• fvm dart scripts/api_check.dart ack 1.1.0 — passed
• git diff --check origin/main...HEAD — passed