[Lyokone]

Description

The CLI only skipped its prompts on CI. Run by a script or an AI coding agent without a terminal (and without CI set), the first prompt waited forever: flutterfire configure and flutterfire install latest with stdin from /dev/null both hung until killed.

The CLI is now non-interactive on CI or when stdin is not a terminal (isNonInteractive in common/utils.dart). stdin.hasTerminal alone is not enough: it is also true for other character devices such as /dev/null, which many tools use as stdin, so stdin's echo mode is read as well (it throws unless stdin is a real terminal).

When non-interactive, each prompt either uses the value given by the flags or exits 1 with an error naming the flag to pass, for example:

NonInteractiveException: Cannot ask which Firebase plugins to install without a terminal attached to stdin. Please re-run the command with the `--plugins` flag, e.g. `--plugins=firebase_core,firebase_auth`, or with the `--only-pubspec-plugins` flag to install the plugins already in your `pubspec.yaml`.

• Every isCI check guarding a prompt now uses isNonInteractive, and the messages name the flag (--platforms, --out, --android-out, --ios-build-config/--ios-target, --overwrite-firebase-options, ...).
• New checks where there were none: install's plugin choice, platform choice, the "reuse firebase.json?" question, an invalid --out, the Apple service file path, and overwriting an existing firebase_options.dart.
• The prompt helpers throw a new NonInteractiveException instead of calling interact as a safety net for any other call site.
• If fetching projects fails, the error is rethrown instead of asking whether to create a project.
• --version skips the update check without a terminal, as it already did on CI.
• README: new "Running without a terminal" section.

Behavior in a terminal is unchanged (checked with a pty). On CI it is unchanged too, except that prompts that used to hang there now fail with an error. Piping answers in (yes | flutterfire ...) never worked with interact and now fails fast instead of hanging.

Testing

• New offline test/non_interactive_test.dart (21 tests): fake stdin through IOOverrides (pipe, /dev/null, terminal), plus the real CLI as a subprocess with stdin piped and from /dev/null. With the fix reverted, 15 of them fail.
• dart analyze --fatal-infos clean, all offline tests pass (89).
• Not run locally: the e2e tests that need FIREBASE_TOKEN, and Windows.

Type of Change

• ✨ feat -- New feature (non-breaking change which adds functionality)
• 🛠️ fix -- Bug fix (non-breaking change which fixes an issue)
• ❌ ! -- Breaking change (fix or feature that would cause existing functionality to change)
• 🧹 refactor -- Code refactor
• ✅ ci -- Build configuration change
• 📝 docs -- Documentation
• 🗑️ chore -- Chore