fix(search): parenthesize group_id OR-chain in multi-group fulltext queries

[Saltasm]

Problem

The Neo4j fulltext query builders join group filters with OR, then append the query terms with AND, without parenthesizing the OR-chain:

group_id:"a" OR group_id:"b" OR group_id:"c" AND (terms)

Lucene's classic query parser treats AND as promoting its adjacent clauses to MUST, so this parses as:

clause	occur
group_id:"a"	SHOULD
group_id:"b"	SHOULD
group_id:"c"	MUST (promoted by the following AND)
(terms)	MUST

A BooleanQuery with any MUST clause requires only the MUST clauses, so this effectively becomes (group_id:"c" AND terms): the leading groups become scoring-only and the query terms are scoped to just the last group_id. A multi-group fulltext search therefore silently returns matches from only the last group passed (and zero rows when that group is empty), while the semantic leg of hybrid search masks the regression.

Fix

Wrap the OR-chain in parens so the terms apply across all groups:

(group_id:"a" OR group_id:"b" OR group_id:"c") AND (terms)

Applied to both Neo4j builders that have the issue:

• graphiti_core/search/search_utils.py — fulltext_query (neo4j branch)
• graphiti_core/driver/neo4j/operations/search_ops.py — _build_neo4j_fulltext_query

Single-group queries are unaffected (group_id:"a" AND (terms) already parses correctly). FalkorDB and Kuzu builders are unaffected — they already parenthesize / use different syntax.

Verification

With the parenthesized query, an identical multi-group search returns the same cross-group result set regardless of the order group_ids are passed; without it, results collapse to whichever group_id is passed last.