feat(query-builder): condition builder for the where clause - #2420

🟢 Confidence 10/10 · safe to merge. Test-only delta on the operator table, pinned against Operator.literals and the engine's group warnings; no production code changed.
_{no findings · tests covered · risk low}

This head adds the two missing pins to the condition builder's operator table: WHERE_OPERATORS is held to the grammar's operator literals, and whereKeyMatchesAnyOf to how the engine actually lowers OR groups. No production behavior changes.

• where-key-rules.test.ts sorts WHERE_OPERATORS against Operator.literals so a grammar operator can't be missed
• Twelve cases run a real OR-group clause through buildTimeseriesQuerySpec per source and key

Fixed since the last review

• ✅ F15 · WHERE_OPERATORS is a hand copy of the domain Operator literals
• ✅ F16 · No case exercises whereKeyMatchesAnyOf, so its OR-group claim is unpinned

_{1ac178f · Reply "won't fix" to dismiss a finding, or mention @maple-review-bot to ask about one.}