Fix OR expression with KNN producing syntax error

[abrookins]

Summary

Fixes #557 - Using an OR expression with a KNN expression was raising ResponseError: Syntax error at offset.

Problem

When combining an OR expression like (Album.tags == "x") | (Album.tags == "y") with a KNN expression, the generated query was invalid:

(@tags:{x})| (@tags:{y})=>[KNN $K @embedding $vec AS score]

The issue is that the KNN suffix =>[KNN ...] was only being applied to the second term of the OR expression, not the entire filter. RediSearch requires the filter to be a single expression before the KNN syntax.

Solution

Always wrap the filter expression in parentheses when appending KNN syntax (unless it's the wildcard *):

((@tags:{x})| (@tags:{y}))=>[KNN $K @embedding $vec AS score]

The previous logic checked startswith("(") to determine if wrapping was needed, but this was insufficient for OR expressions that happen to start with ( but aren't fully wrapped.

Changes

• Fixed FindQuery.query property to always wrap filter expressions in parentheses when combining with KNN
• Added test_or_expression_with_knn test that reproduces the exact scenario from the issue

Testing

The test creates albums with different tags, then queries using:

1. OR expression only (works)
2. KNN only (works)
3. OR expression + KNN (was failing, now works)