[ax] Never emit ANSI when output is not a TTY, even with --ansi

[TomasVotruba]

Why

When output is piped, redirected or captured by an agent, colored output is noise - ANSI escape bytes an agent has to strip. Symfony already drops color on a non-TTY by default, but an explicit --ansi overrides that detection and forces color even into a pipe:

rector process --dry-run --ansi | tee out.txt   # out.txt held raw escape codes

What

Force console decoration off when STDOUT is not a TTY, regardless of --ansi. Real terminals are unaffected (they keep color); only non-interactive output is guaranteed clean.

// SymfonyStyleFactory::create()
if (! (defined('STDOUT') && stream_isatty(STDOUT))) {
    $consoleOutput->setDecorated(false);
}

Same non-TTY detection used for the progress bar in #8444.

Verification

Piping a run with --ansi (2 changed lines):

• before: 12 ANSI escape sequences in the captured output
• after: 0

Plain piped output was already clean (0) and stays 0; interactive terminal output keeps color.

This is env-dependent output plumbing that reads the real STDOUT stream, so it is verified via the CLI before/after rather than a unit test.