fix(validator): resolve inline rule overload

[SrHenry]

Summary

• Fix createInlineRule overload resolution for named rules when only TSubject is explicit
• Add regression coverage for createInlineRule('name', predicate)
• Preserve existing runtime behavior

Closes #40

Verification

• yarn run check
• yarn test
• yarn tsc -p tsconfig.json --noEmit
• yarn build

[SrHenry]

Review follow-up: added missing test coverage for anonymous overload variants

The overload reordering in this fix is correct, but the original test file only covered the 2-argument named forms. Since the fix is fundamentally about overload resolution with explicit type parameters, I've added two test cases:

1. 1-arg anonymous form — createInlineRule((value: string) => value.length > 0) returns Custom.Rule.<anonymous>. Guards against the anonymous overload being shadowed by future overload changes.

2. 1-arg with explicit TSubject — createInlineRule<string>(value => value.length > 0) still resolves to the anonymous overload (not the 2-arg overload). This is the exact pattern used in production at SchemaValidator.spec.ts:147 and is directly relevant to the bug being fixed.

All 4 tests pass, lint is clean.

[SrHenry]

Follow-up: implementation improvements and type-level test coverage

1. Replaced args.reverse() with length-based dispatch

The original implementation used args.reverse() to destructure positional args in reverse order — a non-obvious pattern that relied on in-place array mutation and required type assertions to work. Replaced with a straightforward args.length check that reads left-to-right, matching the overload signatures directly.

Before:

const [predicate, name = InlineRuleName] = args.reverse() as ...

After:

if (args.length === 1) {
  return createRule({ name: InlineRuleName, handler: createRuleHandler(args[0]) })()
}
return createRule({ name: args[0], handler: createRuleHandler(args[1]) })()

This also eliminates the non-null assertion (second!) that was needed with the destructuring approach, fixing a biome lint warning.

2. Removed stale commented-out code

The file had 3 lines of commented-out original implementation at the top that served no purpose.

3. Added expectTypeOf type-level tests

Since this fix is fundamentally a type-level fix (overload resolution), runtime tests alone are insufficient. Added a describe('type inference') block with 5 expectTypeOf assertions covering all overload variants:

Call pattern	Expected rule[0] type
createInlineRule('hasLength', ...)	'hasLength' (literal)
createInlineRule<string>('hasLength', ...)	string (widened)
createInlineRule(predicate)	InlineRuleName
createInlineRule<string>(predicate)	InlineRuleName
createInlineRule<string, 'hasLength'>(...)	'hasLength' (literal)

These assert the exact return type at compile time, catching any future overload regressions that runtime tests would miss.

4. Added runtime test for both-type-params-explicit form

createInlineRule<string, 'hasLength'>('hasLength', ...) was not covered by any test. Added.

All 358 tests pass, lint clean, typecheck clean.