chore(quest): report that a subset compiler would not beat rustc on moq

quest/README.md

@@ -33,4 +33,4 @@ Decided with the maintainer on 2026-10-23, when rust2 was planned from moq
 - [m1: consumers waiting](/quest/m1/README.md) - the exporter that replaces the UniFFI fork for moq
 - [m2: research](/quest/m2/README.md) - the TypeScript translator's spikes and features toward moq-net's model, and the fork's gated work
 - [m3: deferred](/quest/m3/README.md) - the pure-Rust profile and upstream's build-speed levers, measured by the benchmark
-- [m4: long-term research](/quest/m4/README.md) - ideas no consumer needs yet, such as a subset compiler
+- [m4: long-term research](/quest/m4/README.md) - ideas no consumer needs yet, such as a rustc and cargo fork

quest/m4/README.md

@@ -18,8 +18,15 @@ only 7% of moq-net edits
 [moq-dev/rust2#70](https://github.com/moq-dev/rust2/pull/70)).
 [The fork](/quest/m4/fork.md) collects the reasons to change rustc and cargo instead.
 
+Closed on 2026-11-06: a compiler for a stricter Rust subset
+([moq-dev/rust2#615](https://github.com/moq-dev/rust2/pull/615)). 61% of the
+LLVM IR moq's own crates emit is std's and dependencies' generics instantiated
+at moq's types, closures included, so it would have to compile std too. Levers
+that need no new frontend reach its best case: ra-jit already applies the
+moq-net body edits it serves in under half a second, and Cranelift cuts a clean
+build's retired instructions by 16%.
+
 ## Required
 
-- [A subset compiler](/quest/m4/subset-compiler.md) - whether a compiler for a stricter Rust subset can beat rustc on moq's builds, given the verdict that closed it before
 - [Waiting: a rustc and cargo fork](/quest/m4/fork.md) - the evidence ledger for carrying a fork; condition: enough measured reasons to pay for one
 - [moq in pure Go](/quest/m4/go/README.md) - rust2-go translating moq-net, with no cgo, fast enough to replace the cgo bindings for Go users