Fix music file matching: Mvt3 was resolving to Mvt1 for every season

The old pattern *Mvt*3* matched .mp3 in every MP3 filename, so sort|head-1
always picked track 01 (Mvt1). Fix by finding all files for the season
then filtering with grep -iE "Mvt[^0-9]*N[^0-9]", which requires the
movement number to be surrounded by non-digit characters (space, dot,
underscore) and cannot match digits embedded in .mp3 or track prefixes.

https://claude.ai/code/session_01C4jbd3waXG3eKZYbGUjLUQ

montage-mvt.sh

@@ -53,7 +53,8 @@ video_dir="$MOVIES_DIR/$CAM_NAME/$ASTRO_YEAR/$SEASON/Mvt$MVT_NUM"
 output_dir="$video_dir/montage"
 mkdir -p "$output_dir"
 
-music_file=$(find "$music_base_dir" -type f -iname "*${SEASON}*Mvt*${MVT_NUM}*" | sort | head -n 1)
+music_file=$(find "$music_base_dir" -type f -iname "*${SEASON}*" \
+    | grep -iE "Mvt[^0-9]*${MVT_NUM}[^0-9]" | sort | head -n 1)
 if [ -z "$music_file" ]; then
     "$SCRIPT_DIR/notify.sh" "FAILED: montage $SEASON Mvt$MVT_NUM ($ASTRO_YEAR)" \
         "Music file not found in $music_base_dir" || true