improvement(search): fall back to Jira summaries holding half the terms of a longer query - #9115

Summary

• Follow-up to improvement(search): lead an overflowing Jira all-terms match with issues whose summary holds every term #9111: when an overflowing plain Jira search has no issue whose summary holds every term, and the query has three or more distinct terms, issues whose summary holds at least half of them lead the page instead (the same minimum-should-match rule the any-term Jira filter uses)
• The all-terms and half-terms summary searches run in parallel, so the extra round adds one Jira round trip, not two; a failure of either keeps whatever the other found, and both failing keeps today's page and cursor
• Terms are counted the way Jira's stemmed search counts them (a word and its plural once), for both the three-term guard and the filter; two-term queries stay with summaries holding every term (half of two is one word, too loose)
• The half-term search fetches 50 pair matches before filtering, and orders the survivors by how many terms their summary holds
• jiraTextClause takes the field (text or summary), replacing the separate summary helper

Type of Change

• Improvement

Testing

• atlassian.test.ts: 6 new cases (half-terms summaries lead and a summary below half is dropped, two-term and word-plus-plural queries skip the fallback, most terms first, matches beyond the first pair page, a failed half search keeps the all-terms page and cursor); each guard reverted and its test went red, including cancellation through the parallel searches
• Offline replay on a large production Jira (read-only), 60 distinct plain queries from real client sessions, blind relevance judge on the pooled issues: 23 overflow a page; with this follow-up the summary-first rule changes 22; 19 better, 3 equal, 1 slightly worse (10 → 9 relevant); relevant issues in the top 10 33 → 103 (all-terms alone, improvement(search): lead an overflowing Jira all-terms match with issues whose summary holds every term #9111: 41 → 60)

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing (new tests pass the test-audit authoring gate)
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)