release: fix use none as the canonical non-platform label

[callinmullaney]

This PR does the following:

• Replaces generic with none as the canonical platform identifier for projects without platform-specific behavior.
• Defaults missing or empty platform configuration to none.
• Normalizes legacy generic configuration and environment overrides to none.
• Keeps generic as a backward-compatible alias for existing projects.
• Adds and exports noneStorybookAdapter while preserving the existing genericStorybookAdapter export as an alias.
• Keeps unknown platforms on the non-platform adapter behavior without applying Drupal-specific behavior.
• Updates release fixtures, tests, examples, and documentation to use none.
• Adds regression coverage for platform normalization, adapter resolution, project configuration, build output, Storybook behavior, and audit defaults.

Related Issue(s)

• N/A

Notes:

• Existing projects configured with "platform": "generic" will continue to work and will resolve internally to none.
• New and updated projects should use "platform": "none".
• This is a terminology and configuration-alignment change. The non-platform behavior remains the same:
  • Build output stays in dist.
  • Drupal behavior shims and Twig filters are not enabled.
  • Drupal SDC output mirroring is not enabled.
• The Drupal adapter and its behavior are unchanged.
• Unknown platform identifiers continue to use the none adapter behavior while retaining their configured platform name.

Functional Testing:

• Run npm run lint.
• Run npm run test.
• Run npm run fixtures:release.
• Confirm a project with "platform": "none" uses normal dist output and does not enable Drupal behavior.
• Confirm a legacy project with "platform": "generic" resolves to the same none behavior.
• Confirm a project without a configured platform defaults to none.
• Confirm an EMULSIFY_PLATFORM=generic override is normalized to none.
• Confirm Drupal projects continue to use Drupal behavior and SDC output rules.
• Confirm Storybook builds and renders correctly for none, legacy generic, and Drupal fixtures.

Security

No new user-input handling or external execution paths are introduced. This change only normalizes platform identifiers and selects the existing non-Drupal adapter behavior.

Accessibility

No accessibility review is needed. This change does not alter rendered markup, styles, accessibility configuration, or interactive behavior.

[github-actions]

🎉 This PR is included in version 4.0.3 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

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