fix(node-pty): fail loudly on npm install failure; require gcc/make/python3

Two complementary changes that close the silent-failure path surfaced
during testing for #401.

1. install_node_pty: when `npm install node-pty` fails, abort the build
   with an explicit error message that names the likely cause (missing
   C/C++ toolchain or python3) and the per-distro fix command. Previously
   the function printed a one-line warning and continued, which left
   pty_src_dir empty, skipped the entire copy block, and shipped the
   upstream Windows node-pty binaries unchanged — exactly the failure
   mode in #401.

2. check_dependencies: add gcc, g++, make, python3 to the dependency
   check so the build environment is auto-provisioned before
   install_node_pty runs (build-essential on Debian/Ubuntu, gcc /
   gcc-c++ / make / python3 on Fedora). Skipped when --node-pty-dir
   is set (Nix and explicit overrides bring their own pre-built node-pty).

Together: the dep check makes the failure rare, and the install_node_pty
abort makes the rare failure obvious instead of silent.

Verified two ways:

- Isolated test: forced npm to a fake binary that exits 1, called
  install_node_pty, confirmed exit code 1, error message contains the
  Debian/Fedora install hints, and the staging copy block did not run.
- Full deb build: ran build.sh in an ubuntu:24.04 container with no
  pre-installed compilers (only ca-certificates, wget, sudo, nodejs,
  npm). check_dependencies ran `apt install ... build-essential`
  automatically; npm install node-pty subsequently compiled cleanly;
  shipped pty.node is ELF 64-bit LSB shared object, x86-64.

scripts/patches/cowork.sh

@@ -807,12 +807,27 @@ install_node_pty() {
 		echo '{"name":"node-pty-build","version":"1.0.0","private":true}' > package.json
 
 		echo 'Installing node-pty (this compiles native module)...'
-		if npm install node-pty 2>&1; then
-			echo 'node-pty installed successfully'
-			pty_src_dir="$node_pty_build_dir/node_modules/node-pty"
-		else
-			echo 'Failed to install node-pty - terminal features may not work'
+		# Fail loudly on npm install failure rather than warn-and-continue.
+		# The previous behavior silently dropped pty_src_dir, skipped the
+		# entire copy block, and shipped the upstream Windows node-pty
+		# binaries (the #401 failure mode). check_dependencies should now
+		# install gcc/g++/make/python3 before we get here, so this branch
+		# is the last line of defense for build-tool gaps that auto-install
+		# couldn't fix (unknown distro, broken package mirror, etc.).
+		if ! npm install node-pty 2>&1; then
+			echo "Error: 'npm install node-pty' failed." >&2
+			echo 'node-pty has a native module compiled via node-gyp;' >&2
+			echo 'this usually means the build environment lacks a C/C++' >&2
+			echo 'compiler, make, or python3.' >&2
+			echo '' >&2
+			echo 'Install build tools and re-run:' >&2
+			echo '  Debian/Ubuntu: sudo apt install build-essential python3' >&2
+			echo '  Fedora/RHEL:   sudo dnf install gcc gcc-c++ make python3' >&2
+			cd "$project_root" || exit 1
+			exit 1
 		fi
+		echo 'node-pty installed successfully'
+		pty_src_dir="$node_pty_build_dir/node_modules/node-pty"
 	fi
 
 	if [[ -n $pty_src_dir && -d $pty_src_dir ]]; then

scripts/setup/dependencies.sh

@@ -22,16 +22,30 @@ check_dependencies() {
 		rpm) all_deps="$all_deps rpmbuild" ;;
 	esac
 
+	# node-pty has a native C++ module compiled via node-gyp during
+	# `npm install`. Without gcc/g++/make/python3 the install silently
+	# emits a warning, leaves pty_src_dir empty, and the build ends up
+	# shipping the upstream Windows binaries (the #401 failure mode).
+	# Skip when --node-pty-dir is set (Nix and explicit overrides bring
+	# their own pre-built node-pty).
+	if [[ -z ${node_pty_dir:-} ]]; then
+		all_deps="$all_deps gcc g++ make python3"
+	fi
+
 	# Command-to-package mappings per distro family
 	declare -A debian_pkgs=(
 		[p7zip]='p7zip-full' [wget]='wget' [wrestool]='icoutils'
 		[icotool]='icoutils' [convert]='imagemagick'
 		[dpkg-deb]='dpkg-dev' [rpmbuild]='rpm'
+		[gcc]='build-essential' [g++]='build-essential'
+		[make]='build-essential' [python3]='python3'
 	)
 	declare -A rpm_pkgs=(
 		[p7zip]='p7zip p7zip-plugins' [wget]='wget' [wrestool]='icoutils'
 		[icotool]='icoutils' [convert]='ImageMagick'
 		[dpkg-deb]='dpkg' [rpmbuild]='rpm-build'
+		[gcc]='gcc' [g++]='gcc-c++'
+		[make]='make' [python3]='python3'
 	)
 
 	local cmd