Nested property/item constraints inside a oneOf branch are not deeply validated #270

Description

After oneOf support was added (#201 / PR #267), the validator dispatches on schema.type and the traverse walk skips subschemas under the oneOf keyword (so each branch is matched against the parent's data one level deep). That means constraints nested inside a oneOf branch are never deeply validated.

Reproduction

{ "oneOf": [ { "type": "object", "properties": { "a": { "type": "string" } } } ] }

validated against { "a": 42 } — the branch matches (object type) and the invalid nested property a is not flagged.

Expected

Nested property/item constraints within a matching oneOf branch should be validated, not just the branch's top-level type.

No false positives result today, but this is a genuine validation gap worth tracking.