feat: add superderive stepwise derivation figures

A third sibling toolkit: rewrite steps, justification rails, cancel/substitute highlights, and lint-on-warning builds.
2026-08-17 10:05:03 +08:00
commit 9f635d358b
22 changed files with 724 additions and 0 deletions
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+# Layout
+
+Place by cursor inside `\sdrow` … `\sdrowend`. Never hand-tune a neighbour with a magic offset. If a reason does not fit, move the step to the next row.