fix: discriminate overloaded function args

[FarajiOranj]

Summary

Closes #132.

Makes the inferred args type for overloaded functions (and events) a
discriminated union, so only the arguments of a single overload can be used at a
time.

Before, for an overloaded foo(uint256 num) / foo(string name):

type FooArgs = FunctionArgs<OverloadedAbi, "foo">;
//   ^? { num: bigint } | { name: string }

client.read({ abi, address, fn: "foo", args: { num: 123n, name: "abc" } });
//                                            ^ both allowed (the bug)

After:

type FooArgs = FunctionArgs<OverloadedAbi, "foo">;
//   ^? OneOfNamed<{ num: bigint } | { name: string }>

client.read({ abi, address, fn: "foo", args: { num: 123n, name: "abc" } });
//                                                         ^ Type 'bigint' is not
//                                                           assignable to type 'undefined'

Changes

• AbiObjectType (in Abi.ts) now wraps its result in a discriminated union.
  This flows into FunctionArgs, ConstructorArgs, and EventArgs (all args).
  FunctionReturn uses AbiSimplifiedType and is intentionally unchanged, so
  return values stay a plain union.
• Added two type utilities: OneOfNamed and NamedUnionKey. OneOfNamed is
  like the existing OneOf, but it only counts named keys when negating other
  members and returns a non-union type unchanged. This keeps it correct when an
  overload set includes a no-arg signature (whose "empty" object would otherwise
  poison the other members with [x: string]: undefined index signatures), and
  avoids changing the widely-used OneOf (so CallParams/prepareCall etc. are
  unaffected).

Tests

Added Function.test-d.ts type-tests covering discrimination for overloads with
different arg names, different arity, shared names, and a no-arg-plus-named
overload set, plus no-regression checks for single/no-arg functions and
FunctionReturn. This is a type-only change, so the runtime suite is unchanged.

[changeset-bot]

🦋 Changeset detected

Latest commit: 01df456

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@gud/drift	Patch
@gud/drift-ethers-v5	Patch
@gud/drift-ethers	Patch
@gud/drift-viem	Patch
@gud/drift-web3	Patch

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