fix(falkordb): episode_mentions_reranker inverted ordering and min_score bypass

[Naseem77]

What it fixes

Two related bugs in FalkorSearchOperations.episode_mentions_reranker (graphiti_core/driver/falkordb/operations/search_ops.py):

1. Ranking is inverted

Scores are episode-mention counts (higher = more relevant), but the sort was ascending, so the least-mentioned nodes ranked first. A node mentioned by 3 episodes ranked below a node mentioned by 1.

2. Unmentioned nodes bypass min_score

Nodes with no MENTIONS edges were given float('inf') as a score, which passes any min_score threshold (and, combined with the ascending sort, also pushed them to the end rather than filtering them). They now score 0, so any positive min_score filters them out.

Related: #1342 reported the inverted ordering for the legacy search_utils.py path (fix pending in #1640/#1512), but this ops-layer copy has the same bugs and is not covered by those PRs.

Before / after

With Popular mentioned by 3 episodes, Rare by 1, Unmentioned by 0:

await driver.search_ops.episode_mentions_reranker(driver, uuids)
# before: ['Rare', 'Popular', 'Unmentioned']
# after:  ['Popular', 'Rare', 'Unmentioned']

await driver.search_ops.episode_mentions_reranker(driver, uuids, min_score=2)
# before: ['Popular', 'Unmentioned']   (inf >= 2)
# after:  ['Popular']

Validation

• New FalkorDB integration test covering both ordering and min_score; verified it fails on the unfixed code and passes with the fix
• Full tests/driver suite passes against a live FalkorDB

[zep-cla-assistant]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}