dcd1836d51
- Added `isTerminalHeadless()` / `setTerminalHeadless()` to `env`, a process-wide switch that suppresses real-terminal side effects (stdout escape/frame writes, stdin raw mode, CSI/OSC probes, SIGWINCH, window-title changes, emergency restore). - Defaulted the flag to `isBunTestRuntime()` so it engages when `bun test` sets `NODE_ENV=test`, and made `setTerminalHeadless` return the previous value so callers can restore exact prior state.