BUGFIX: Make --help display command overview

[w3lld1]

./flow --help now displays the same command overview as ./flow help instead of the abbreviated help stub.

The request builder keeps the existing no-argument behavior and routes only the explicit top-level --help option to the full help command. A regression test covers the alias.

Fixes #3583

Upgrade instructions

None.

Review instructions

Run the focused request-builder unit test and verify that ./flow --help lists the available commands.

Validation

• vendor/bin/phpunit --bootstrap /tmp/neos-unit-bootstrap.php Neos.Flow/Tests/Unit/Cli/RequestBuilderTest.php --colors=never — 30 tests, 107 assertions
• php -l Neos.Flow/Classes/Cli/RequestBuilder.php
• php -l Neos.Flow/Tests/Unit/Cli/RequestBuilderTest.php

The full development-distribution CI matrix was not reproduced locally.

Checklist

• Code follows the PSR-2 coding style
• Tests have been created, run and adjusted as needed
• The PR is created against the lowest maintained branch
• PR title is brief but complete and starts with FEATURE|TASK|BUGFIX
• The first section explains the change briefly for change-logs
• No breaking changes