fix(query-engine): keep list inputs from nesting SQL past max_parser_depth - #2021

🟢 Confidence 10/10 · safe to merge. Flattening is provably semantics-preserving here, and a property test, the SQL baseline and a 500-repository e2e pin it.
_{no findings · tests covered · risk medium}

Replaces the per-item .and()/.or() chains in four query-engine builders — CI actor stats, log body search, attribute-filter OR groups and funnel steps — with one flat CH.and/CH.or call, so parser nesting no longer grows with the list. The SQL is unchanged apart from parentheses.

• ciActorStatsQuery ORs default branches with one flat CH.or
• Log body search ANDs every token through one CH.and
• buildAttrFilterCondition OR groups and funnel steps flatten their OR
• New property test bounds nesting for 7 list-taking builders; e2e covers 500 repos

_{56e9da6 · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}