Fix fake index assertion callback semantics

[stevebauman]

What changed

• Make assertCreated() match the recorded index by name when no callback is provided.
• Treat callbacks passed to assertCreated(), assertMappingPut(), and assertSettingsPut() as predicates against the actual recorded mapping and settings.
• Make mapping and settings callbacks optional so callers can assert only that the operation occurred.
• Require OpenSearchAdapter ^1.2.1 for the corresponding fake assertion support.
• Add coverage for successful predicates and predicates that return false.

Why

The fake previously used assertion callbacks as builders for a second expected mapping or settings object. A name-only assertion could therefore fail when the recorded index contained fields that the assertion did not reproduce. This differs from Laravel fake assertions, where a callback inspects the operation that was actually dispatched and returns whether it matches.

Developer impact

Assertions can now focus on the operation:

$index->assertCreated('users');
$index->assertMappingPut('users');
$index->assertSettingsPut('users');

A predicate can be added only when the recorded definition needs further inspection.

Dependency

Depends on DirectoryTree/OpenSearchAdapter#4. The adapter should be released as v1.2.1 before this package is released.

Validation

• vendor/bin/pint
• vendor/bin/pest — 96 tests, 205 assertions on the master-based branch
• git diff --check