[skyzhao1223]

Fixes a NaN/Inf score bug in the Elasticsearch search store.

Problem

parseSearchResult normalized every hit's score by the first hit's _score:

score := float64(ptr.From(hit.Score_))
if i == 0 {
    firstScore = score
}
doc.WithScore(score / firstScore)

When the first hit's _score is 0 (e.g. constant-score or filter context with no ranking), 0/0 produces NaN for the first hit and Inf for the rest, corrupting downstream score-based sorting and threshold filtering.

Fix

Fall back to the raw score when the first score is 0 (there is nothing to normalize against):

if firstScore != 0 {
    doc.WithScore(score / firstScore)
} else {
    doc.WithScore(score)
}

Tests

elasticsearch_searchstore_test.go adds:

• TestParseSearchResultZeroScore: zero scores produce no NaN (fails on old code).
• TestParseSearchResultNormalizesScore: [2,4,1] normalizes to [1,2,0.5].

go test ./infra/document/searchstore/impl/elasticsearch/ -run TestParseSearchResult