fix: date filter parameters collide across OR clauses

[totto]

What

In build_edge_search_filter_query(), date filter parameters are keyed by only the inner-loop index j, not by the outer OR-clause index i:

for i, or_list in enumerate(filters.valid_at):
    for j, date_filter in enumerate(or_list):
        filter_params['valid_at_' + str(j)] = date_filter.date  # ← bug

When filters.valid_at has more than one OR clause, each clause resets j to 0. OR clause 1 overwrites OR clause 0's parameter values. The Cypher query then uses the wrong date values for all but the last OR clause.

Why it matters

Any temporal filter with multiple OR conditions silently applies the last clause's dates to all clauses, producing incorrect query results without any error.

The same bug exists in all four date fields: valid_at, invalid_at, created_at, expired_at.

Fix

Key by both i (OR-clause) and j (AND-condition within clause):

filter_params[f'valid_at_{i}_{j}'] = date_filter.date
# query uses: f'$valid_at_{i}_{j}'

Applied to all four date fields.

Reproducer

from datetime import datetime
from graphiti_core.search.search_filters import EdgeSearchFilters, DateFilter
from graphiti_core.search.search_filters import ComparisonOperator, build_edge_search_filter_query

d1 = datetime(2024, 1, 1)
d2 = datetime(2025, 1, 1)

filters = EdgeSearchFilters(
    valid_at=[
        [DateFilter(date=d1, comparison_operator=ComparisonOperator.gt)],
        [DateFilter(date=d2, comparison_operator=ComparisonOperator.lt)],
    ]
)
_, params = build_edge_search_filter_query(filters, "neo4j")
# Before fix: params == {'valid_at_0': d2}   ← d1 lost
# After fix:  params == {'valid_at_0_0': d1, 'valid_at_1_0': d2}  ✓

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[totto]

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