fix: auto-detect terminal color support instead of forcing it

FORCE_COLOR defaulted to 1, emitting ANSI codes unconditionally. On SSH
sessions without a proper TTY or with TERM=dumb this caused color codes
to render text invisible. Now colors are enabled only when stdout is an
interactive terminal; FORCE_COLOR=1 can still override when needed.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/arty.sh

@@ -16,8 +16,12 @@ WHIP_CONFIG="${WHIP_CONFIG:-arty.yml}"
 WHIP_HOOKS_DIR=".whip/hooks"
 WHIP_CHANGELOG="${WHIP_CHANGELOG:-CHANGELOG.md}"
 
-# Colors for output - only use colors if output is to a terminal or if FORCE_COLOR is set
+# Enable colors only when stdout is a real terminal (or FORCE_COLOR=1 overrides)
+if [[ -t 1 && "${TERM:-}" != "dumb" ]]; then
   export FORCE_COLOR=${FORCE_COLOR:-"1"}
+else
+  export FORCE_COLOR=${FORCE_COLOR:-"0"}
+fi
 if [[ "$FORCE_COLOR" = "0" ]]; then
   export RED=''
   export GREEN=''