fix(build): declare VARIANT in local script half (was remote-only)

The VARIANT variable was set inside the REMOTE_SCRIPT heredoc for
naming artifacts during the cargo tauri build, but never declared
in the local half of the script where it's used to rename downloaded
files. Under `set -u` strict mode this aborted the local downloads
with "unbound variable: VARIANT" after a successful remote build.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

scripts/build-linux-desktop-docker.sh

@@ -31,7 +31,7 @@ SSH_OPTS="-o ConnectTimeout=15 -o ServerAliveInterval=15 -o ServerAliveCountMax=
 REBUILD_RUST=0
 DO_PULL=1
 IMAGE_BUILD=0
-# WITH_AEC=1 enables the wzp-client `linux-aec` feature (WebRTC AEC3 via
+# WITH_AEC=1 enables the wzp-client `linux-aec` feature (WebRTC AEC via
 # webrtc-audio-processing) and renames the output artifacts with an `-aec`
 # suffix so both variants can coexist on disk.
 WITH_AEC=0
@@ -49,6 +49,15 @@ for arg in "$@"; do
     esac
 done
 
+# Variant suffix used locally to rename downloaded artifacts so the noAEC
+# baseline and the AEC build can coexist in $LOCAL_OUTPUT. Mirrors the
+# same VARIANT declaration inside the remote REMOTE_SCRIPT heredoc.
+if [ "$WITH_AEC" = "1" ]; then
+    VARIANT="aec"
+else
+    VARIANT="noAEC"
+fi
+
 log() { echo -e "\033[1;36m>>> $*\033[0m"; }
 ssh_cmd() { ssh $SSH_OPTS "$REMOTE_HOST" "$@"; }