quest: plan NonZero's unchecked arithmetic

quest/m3/ts-unsafe/README.md

@@ -78,5 +78,6 @@ Public API: the translator's output.
 - [BinaryHeap from std's MIR](/quest/m3/ts-unsafe/binary-heap-mir.md) - std's `BinaryHeap` and `PeekMut` translate, replacing the runtime's port
 - [A slice's pointer cast to an array's](/quest/m3/ts-unsafe/array-casts.md) - `*(s as *const [u8] as *const [u8; N])` in a crate's own code, and `IoSlice`
 - [Unchecked integer operations](/quest/m3/ts-unsafe/unchecked-ops.md) - `unchecked_*` and `NonZero::new_unchecked` translate, aborting on a violated precondition
+- [NonZero's unchecked arithmetic](/quest/m3/ts-unsafe/nonzero-unchecked-ops.md) - `NonZero::unchecked_add` and `unchecked_mul` translate, aborting at std's site
 - [UnsafeCell's raw accessors](/quest/m3/ts-unsafe/unsafecell.md) - `UnsafeCell::raw_get`, `from_mut`, and `replace` translate
 - [A Box of one uninitialized value](/quest/m3/ts-unsafe/box-new-uninit.md) - `Box::new_uninit` and `new_zeroed` for one value translate, through `write` and `assume_init`

quest/m3/ts-unsafe/nonzero-unchecked-ops.md

@@ -0,0 +1,19 @@
+# [XS] NonZero's unchecked arithmetic
+
+## Goal
+
+[rust2-ts](/ts/README.md) translates `NonZero::unchecked_add` and `NonZero::unchecked_mul`,
+proven by differential tests against native Rust. Today each is refused by name.
+
+## Plan
+
+Left by [#622](https://github.com/moq-dev/rust2/pull/622), which translated the integers'
+`unchecked_*` and `NonZero::new_unchecked` through `rs.precondition`. Both are unstable
+(`nonzero_ops`) and not `#[track_caller]`, so a violated precondition aborts with std's
+`unsafe precondition(s) violated` text located inside std's source, through `caller.rs`'s
+`SITES`, rather than at the call.
+
+Decided with the maintainer on 2026-11-07: ✅ m3, in this epic (rejected: skip). No
+consumer at the moq pin.
+
+Public API: the translator's output.