feat: Use flexible layout for columns > 4 without minColumnWidth

[ekatza]

Description

This change enables ColumnLayout to automatically use flexible layout when more than 4 columns are specified without an explicit minColumnWidth prop. Previously, flexible layout was only used when minColumnWidth was set, limiting the component to 4 columns maximum in grid mode.

The change modifies the condition in src/column-layout/internal.tsx to use FlexibleColumnLayout when either minColumnWidth is provided OR columns > 4.

Related links, issue #, if available: AWSUI-61702

How has this been tested?

• Added unit test in src/column-layout/__tests__/column-layout.test.tsx verifying that 5 columns render correctly without minColumnWidth
• Added integration test in src/column-layout/__tests__/with-css.test.tsx verifying flexible layout is used with 5 columns
• Added test case to pages/column-layout/min-width.permutations.page.tsx for visual validation

To validate manually:

1. View the deployed dev pages from the CI pipeline (click "View deployment" link)
2. Navigate to /light/column-layout/min-width-permutations
3. Verify the 5-column layout renders correctly using flexible layout

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates. - Updated JSDoc comments in interfaces.ts to remove 4-column limitation and document behavior for 5+ columns
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md. - Fully backward-compatible; only affects new use case (columns > 4 without minColumnWidth). Previous 5+ columns without minColumnWidth set was not supported.
• Changes do not include unsupported browser features, see CONTRIBUTING.md. - Uses existing FlexibleColumnLayout implementation
• Changes were manually tested for accessibility, see accessibility guidelines. - Uses existing accessible FlexibleColumnLayout component

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function. - n/a

Testing

• Changes are covered with new/existing unit tests? - New unit test added
• Changes are covered with new/existing integration tests? - n/a - component has no integration tests; unit tests should be sufficient for this change

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.42%. Comparing base (87a3e47) to head (cb1776b).
⚠️ Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4260      +/-   ##
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+ Coverage   97.35%   97.42%   +0.06%     
==========================================
  Files         888      891       +3     
  Lines       26031    26099      +68     
  Branches     9411     9435      +24     
==========================================
+ Hits        25343    25427      +84     
- Misses        641      666      +25     
+ Partials       47        6      -41     

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[NathanZlion]

hey @ekatza, Thanks for opening the pull request and taking time to contribute! After taking a closer look and doing some research about how this is used by customers, we found out that there are quite a few teams who are using columns of more than 4 without specifying minColumnWidths. While your fix addresses the spacing issue, automatically switching to FlexibleColumnLayout would introduce unexpected visual changes to their existing implementations. And since there's a documented workaround (setting minColumnWidth when using more than 4 columns), we've decided not to move forward with this change to maintain backwards compatibility.

We appreciate you bringing this to our attention. If you have any questions or want to discuss alternative approaches, feel free to reach out.