fix(common.sh): use tty open test instead of -r for no-TTY detection

macOS /dev/tty passes -r check even when unusable in non-TTY sessions;
replace with `true < /dev/tty` probe so confirm_destructive and
confirm_exact_match correctly detect missing TTY and emit the expected
error message instead of crashing with "Device not configured".

scripts/lib/common.sh

@@ -158,7 +158,7 @@ confirm_destructive() {
     if [[ "${GITEA_YES:-0}" == "1" ]]; then
         return 0
     fi
-    if [[ ! -r /dev/tty ]]; then
+    if ! { true < /dev/tty; } 2>/dev/null; then
         log_err "需要確認但無 TTY；請加 -y / --yes 或設定 GITEA_YES=1"
         exit 1
     fi
@@ -178,7 +178,7 @@ confirm_exact_match() {
     if [[ "${GITEA_YES:-0}" == "1" ]]; then
         return 0
     fi
-    if [[ ! -r /dev/tty ]]; then
+    if ! { true < /dev/tty; } 2>/dev/null; then
         log_err "需要確認但無 TTY；請加 -y / --yes 或設定 GITEA_YES=1"
         exit 1
     fi