Scope update-neovim.sh to debian: arch gets neovim from pacman; guard no-ops elsewhere

run_once_20-install-user-packages.sh.tmpl

@@ -200,8 +200,54 @@ if command -v bun >/dev/null 2>&1; then
     fi
 fi
 
-# Neovim comes from the system package (pacman list above); topgrade keeps
-# it current. No manual tarball install.
+# Neovim — debian apt ships a stale version, so install the official
+# binary tarball, pinned to a known-good version. Bump
+# NVIM_TARGET_VERSION here and in ~/.local/bin/update-neovim.sh to
+# upgrade (topgrade runs the script on debian machines).
+NVIM_TARGET_VERSION="v0.11.4"
+ARCH="$(uname -m)"
+case "$ARCH" in
+    x86_64)
+        NVIM_TARBALL="nvim-linux64.tar.gz"
+        NVIM_EXTRACT_DIR="nvim-linux64"
+        ;;
+    aarch64|arm64)
+        NVIM_TARBALL="nvim-linux-arm64.tar.gz"
+        NVIM_EXTRACT_DIR="nvim-linux-arm64"
+        ;;
+    *)
+        die "unsupported arch for neovim tarball: $ARCH"
+        ;;
+esac
+
+if command -v nvim >/dev/null 2>&1; then
+    INSTALLED_VER="$(nvim --version 2>/dev/null | head -1 | awk '{print $2}')"
+    if [[ "$INSTALLED_VER" == "$NVIM_TARGET_VERSION" ]]; then
+        log "neovim $INSTALLED_VER matches target — skipping"
+        NVIM_TARBALL=""
+    else
+        log "neovim $INSTALLED_VER != target $NVIM_TARGET_VERSION — upgrading"
+    fi
+fi
+
+if [[ -n "$NVIM_TARBALL" ]]; then
+    log "downloading neovim $NVIM_TARGET_VERSION ($NVIM_TARBALL)"
+    cd /tmp
+    if ! curl -fL --retry 3 \
+        "https://github.com/neovim/neovim/releases/download/${NVIM_TARGET_VERSION}/${NVIM_TARBALL}" \
+        -o nvim.tar.gz; then
+        die "failed to download neovim tarball"
+    fi
+    sudo rm -rf /opt/nvim-linux* /usr/local/bin/nvim
+    sudo tar -xzf nvim.tar.gz -C /opt/
+    sudo ln -sf "/opt/${NVIM_EXTRACT_DIR}/bin/nvim" /usr/local/bin/nvim
+    rm -f nvim.tar.gz
+fi
+
+# Verify neovim is reachable (PATH may need /usr/local/bin explicitly for this run)
+if ! command -v nvim >/dev/null 2>&1 && [[ -x /usr/local/bin/nvim ]]; then
+    export PATH="/usr/local/bin:$PATH"
+fi
 
 {{ else -}}
 die "unsupported os_family: {{ .os_family }}"