Fix modal fading issue

[madalynbartman]

Closes #29247

What I did

• Add default onInteractOutside event handler to prevent the modal from closing unexpectedly.

• Make sure handleInteractOutside event parameter matches expected types.

• Update modal component to only perform onInteractOutside if an actual handler is provided. Otherwise, default to no-op.

Checklist for Contributors

Testing

The changes in this PR are covered in the following automated tests:

• stories
• unit tests
• integration tests
• end-to-end tests

Manual testing

This section is mandatory for all contributions. If you believe no manual test is necessary, please state so explicitly. Thanks!

1. Run a Sandbox
2. Go to http://localhost:6006/?path=/story/components-modal--default
3. Verify clicking outside the modal does not close it unexpectedly or cause any fading issues
4. Repeat with remaining modals under the Modal drop down
5. Look at the console logs to ensure the onInteractOutside event handler is triggered correctly when interacting outside the modal

Documentation

• Add or update documentation reflecting your changes
• If you are deprecating/removing a feature, make sure to update
  MIGRATION.MD

Checklist for Maintainers

• When this PR is ready for testing, make sure to add ci:normal, ci:merged or ci:daily GH label to it to run a specific set of sandboxes. The particular set of sandboxes can be found in code/lib/cli-storybook/src/sandbox-templates.ts

• Make sure this PR contains one of the labels below:

  Available labels

  • bug: Internal changes that fixes incorrect behavior.
  • maintenance: User-facing maintenance tasks.
  • dependencies: Upgrading (sometimes downgrading) dependencies.
  • build: Internal-facing build tooling & test updates. Will not show up in release changelog.
  • cleanup: Minor cleanup style change. Will not show up in release changelog.
  • documentation: Documentation only changes. Will not show up in release changelog.
  • feature request: Introducing a new feature.
  • BREAKING CHANGE: Changes that break compatibility in some way with current major version.
  • other: Changes that don't fit in the above categories.

🦋 Canary release

This PR does not have a canary release associated. You can request a canary release of this pull request by mentioning the @storybookjs/core team here.

core team members can create a canary release here or locally with gh workflow run --repo storybookjs/storybook canary-release-pr.yml --field pr=<PR_NUMBER>

Greptile Summary

Fixes modal fading and interaction issues by modifying CSS animations and event handling to prevent unintended behavior when interacting outside the modal.

• Added explicit opacity: 1 and transition: none to Overlay and Container components in /code/core/src/components/components/Modal/Modal.styled.tsx
• Added default onInteractOutside handler in /code/core/src/components/components/Modal/Modal.tsx to prevent unexpected modal closing
• Updated modal component to only trigger onInteractOutside when handler is provided
• Fixed issue where screen would become unclickable when interacting with elements outside modal

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[greptile-apps]

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[greptile-apps]

style: consider using a CSS custom property for the opacity value to make it more maintainable

[greptile-apps]

LGTM

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