feat: ship an Inno Setup installer from the windows release job

windows/installer.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/env bash
+# Pack the dist/ bundle into carrier-windows-<version>-setup.exe.
+#
+# Run from the carrier checkout after windows/bundle.sh has produced
+# dist/. Requires Inno Setup 7 (per-user install, which its own
+# installer's "just me" option produces).
+set -euo pipefail
+
+say() { printf '\n==> %s\n' "$*"; }
+die() { printf '\n!! %s\n' "$*" >&2; exit 1; }
+
+# MSYS2's login shells prune LOCALAPPDATA from the environment, so fall
+# back to cygpath (CSIDL 28 = local AppData of the current user).
+if [ -n "${LOCALAPPDATA:-}" ]; then
+    appdata=$(cygpath -u "$LOCALAPPDATA")
+else
+    appdata=$(cygpath -F 28)
+fi
+ISCC="$appdata/Programs/Inno Setup 7/ISCC.exe"
+[ -f "$ISCC" ] || die "Inno Setup not found at $ISCC — install it from https://jrsoftware.org/isdl.php"
+
+[ -d dist ] || die "no dist/ bundle — run windows/bundle.sh first"
+
+version=$(sed -n 's/^version = "\(.*\)"$/\1/p' Cargo.toml | head -1)
+
+say "compiling the installer"
+# MSYS2_ARG_CONV_EXCL stops MSYS2 mangling /DVersion into a path.
+MSYS2_ARG_CONV_EXCL="*" "$ISCC" /DVersion="$version" windows/carrier.iss \
+    || die "ISCC failed"
+
+say "done — carrier-windows-$version-setup.exe (in the checkout root)"