feat: Show IDE/agent selection first and require a selection in serverpod create - #5819

Users of the serverpod create TUI reached the multi-select screens without learning that Space selects and Enter continues, because the first screen (Project Type) had a default and could be passed with Enter alone. This makes the IDE/agent screen the first screen and blocks moving on until something is selected, matching serverpod quickstart.

• The IDE/agent screen is first and can not be passed without a selection. This covers Enter, Space on a focused Next, and clicking Next.
• Added a "None" option that can not be combined with an editor, so users who do not want agent configuration can still continue. Quickstart and the upgrade path get it too.
• The header hint now reads "Space or click to select · Enter to continue".
• Removed requireIde. The rule is declared on the form config and enforced by serverpod_tui 0.13.0 (feat: Add required selections and exclusive options to forms serverpod_tui#34).

Non-interactive serverpod create is unchanged.

Fixes #5788

Pre-launch Checklist

• I read the Contribute page and followed the process outlined there for submitting PRs.
• This update contains only one single feature or bug fix and nothing else. (If you are submitting multiple fixes, please make multiple PRs.)
• I read and followed the Dart Style Guide and formatted the code with dart format.
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///), and made sure that the documentation follows the same style as other Serverpod documentation. I checked spelling and grammar.
• I added new tests to check the change I am making.
• All existing and new tests are passing.
• Any breaking changes are documented below.

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Breaking changes

None