neovim had no macOS install path at all — it always tried the Linux tarball

Asked to check how the script installs Neovim on Mac, and the answer was: it doesn't.
nvim_install() had zero `$OS` branching, so on macOS it unconditionally fetched
nvim-linux-<arch>.tar.gz — a URL that 404s there. Not a hard crash: the caller's
`if nvim_install; then … else warn …` catches it and reports "Neovim: install failed"
rather than aborting the run, which is exactly the shape that's easy to miss in a long
scrollback. brew has a current, real neovim formula (0.12.5), so that's the macOS
branch — no keg-only linking needed, unlike the Postgres client fix.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

scripts/setup/machine-setup/lib/dev.sh

@@ -155,7 +155,19 @@ nvim_latest_version() {
 #
 # The old install is removed only after the download has succeeded, so a failed
 # fetch leaves the working copy alone.
+#
+# This had NO macOS branch at all until it was caught here: unconditionally fetched
+# nvim-linux-<arch>.tar.gz regardless of $OS, which 404s on a Mac. Not a crash — the
+# caller's `if nvim_install; then … else warn …` catches the failure and reports it as
+# ERRORS+=("Neovim: install failed") rather than aborting the run — but Neovim never
+# actually landed. brew has a real, current formula, so that's the macOS path instead of
+# reaching for a macOS release asset the way lazygit's fix did.
 nvim_install() {
+  if [[ "${OS:-}" == "macos" ]]; then
+    brew install neovim
+    return
+  fi
+
   local asset tarball dest
   asset="$(nvim_asset)"
   tarball="/tmp/nvim-linux-${asset}.tar.gz"