Panic in readFold.reads on a node kind it has no case for

reads.go

@@ -97,6 +97,9 @@ func (f *readFold) reads(n node) []pathRead {
 		out = f.rowReads(n.t, func(b *branches, row int) bool { return b.enter(n.t, row) })
 	case *tableColumn:
 		out = f.cellReads(n, func(b *branches, row int) bool { return b.enter(n.t, row) })
+	case *folder, *nullItem:
+	default:
+		panic(internalError("reads has no case for node %T", n))
 	}
 	out = distinct(out)
 	f.memo[n] = out

todo.md

@@ -40,8 +40,6 @@ maintainer chose on 2026-09-30 to go on with the path steps regardless.
 
 This round, in order:
 
-- Give `readFold.reads` a `default` that panics, as every other switch over node kinds
-  does: a new kind contributes no reads and the draw fence passes it silently.
 - Correct `rowReads`' "checkOwnFamily's refusal, which runs first": `checkNodeFences`
   runs `checkDrawGroup`, which folds through it, before `checkOwnFamily`.
 - Compile each path once at link into steps holding no pointer, with its leaves and