fix: move msg file inside worktree to avoid external_directory permission error

skills/kugetsu/scripts/kugetsu-session.sh

@@ -379,7 +379,7 @@ cmd_start() {
     
     cd "$worktree_path"
     local sanitized_id=$(echo "$new_session_id" | sed 's/[^a-zA-Z0-9_-]/_/g')
-    local msg_file="$LOGS_DIR/msg-$sanitized_id.txt"
+    local msg_file="$worktree_path/.kugetsu-msg.txt"
     printf '%s' "$dev_message" > "$msg_file"
     nohup sh -c "GITEA_TOKEN='${GITEA_TOKEN:-}' opencode run '@$msg_file' --session '$new_session_id'" >> "$LOGS_DIR/dev-$sanitized_id.log" 2>&1 &
     rm -f "$msg_file"
@@ -446,7 +446,7 @@ cmd_continue() {
     
     cd "$worktree_path"
     local sanitized_id=$(echo "$opencode_session_id" | sed 's/[^a-zA-Z0-9_-]/_/g')
-    local msg_file="$LOGS_DIR/msg-$sanitized_id.txt"
+    local msg_file="$worktree_path/.kugetsu-msg.txt"
     printf '%s' "$message" > "$msg_file"
     nohup sh -c "GITEA_TOKEN='${GITEA_TOKEN:-}' opencode run '@$msg_file' --session '$opencode_session_id'" >> "$LOGS_DIR/dev-$sanitized_id.log" 2>&1 &
     rm -f "$msg_file"