feat(editor): drag a Library/History query into the editor as a ( … ) subquery

[BorisTyshkevich]

What

Saved-query (Library) and History rows are now draggable. Dropping one onto the SQL editor inserts that query's SQL wrapped in parentheses as a subquery, at the drop position, undoably. No runtime macro, no library coupling — the SQL you see is the SQL you run (the simplest take on the composable-queries idea in #39).

How

Extends the existing schema-identifier drag path rather than inventing a new one:

• src/ui/editor.js — adds SUBQUERY_MIME next to IDENT_MIME, and a branch in the existing textarea drop handler. The schema-identifier branch is unchanged (still inserts at the caret); the new branch wraps via toSubquery and inserts at the drop point using the existing offsetAt (client coords → text offset, handles padding/scroll/zoom) + replaceRange (undoable), falling back to the caret when the drop lands past the text (e.g. the blank area below the last line).
• src/core/format.js — pure toSubquery(sql): trims, strips a trailing ; and a trailing FORMAT <name> clause (invalid inside ()), brackets the SQL on its own lines; empty input → '' (no-op).
• src/ui/saved-history.js — .saved-row / .history-row get draggable + a dragstart that puts the SQL on SUBQUERY_MIME (mirrors schema.js's dragProps).

Tests

• format.js 100% (toSubquery wrap / strip ; / strip trailing FORMAT / keep non-trailing FORMAT / empty).
• editor.js — drop with SUBQUERY_MIME: inserts at the drop offset (position branch), fallback to caret when past the text, and no-op on empty SQL.
• saved-history.js — saved + history rows are draggable and carry the right SUBQUERY_MIME payload on dragstart.
• e2e (editor-insert.spec.js) — real DataTransfer + DragEvent('drop') over the textarea exercises the actual offsetFromXY geometry happy-dom can't.

820 unit tests pass; coverage gate holds.

Verified live (otel)

Dragging a Library row onto the editor dropped (\nSELECT * FROM claude_otel.otel_logs\n) at the drop position with the surrounding text preserved; dropping in the editor padding fell back to the caret. Deployed to otel for review.

🤖 Generated with Claude Code