The QA1/QA2 design: an `explain` prefix command over
`show data` / `update` / `delete` that runs
EXPLAIN QUERY PLAN (without executing the statement) and
renders the result as an annotated tree. Plan steps keep
the engine's own wording; an annotation taxonomy marks
full scans, index use, and the automatic-index "you
should add an index here" case. Introduces a general
styled-output-line mechanism — an OutputLine may carry
per-span styling — realising the per-span theming
ADR-0016 deferred; the plan renderer is its first
consumer. The explained SQL is shown above the tree as
standard, copy-pasteable SQL.
- docs/adr/0028-query-plans.md — the ADR.
- docs/adr/README.md — index entry.
- docs/requirements.md — QA2 [~] -> [ ]; QA1 note
reconciled (designed in ADR-0028).
claude@clouddev1
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