fix: Remove screen reader specific navigation grid

[avinashbot]

Description

Noticed while going through repos that I had a fix for this I hadn't committed... whoops. The board and item palette have a secret grid based on a table layout that's specially accessible only through screen readers. But this has reportedly ended up confusing more people than it has helped. We got this from an internal ticket, but also validated this within our own team and with some accessibility specialists who all agreed it's fine to get rid of.

On the other hand, it will remove the ability for non-visual users to understand the relative positioning of board items, but it's probably really hard to make the grid feel intuitive in the first place without a text-based prelude for keyboard users. Plus, linear/heading navigation has always worked and will continue to work just fine. Fully non-visual screen reader users will presumably see the "drag"/"resize" buttons and not particularly care.

Oh, and one more thing: I have format-on-save enabled, and for some reason whatever VS Code seems to be doing is disagreeing with what ESLint wants, so I made that discrepancy clearer in .prettierrc. Same thing about tsconfig.json: setting a moduleResolution of "NodeNext" is probably not the right answer for a frontend library (either "Bundler" or "Node" seems correct).

Related links, issue #, if available: AWSUI-37270

How has this been tested?

I, uh, expected some tests to fail. And uh, none did. So I guess I'm increasing code coverage? 😅

Otherwise, I just manually tested things on VoiceOver.

Review checklist

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

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 93.42%. Comparing base (f76c386) to head (0ffc8f5).

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #307      +/-   ##
==========================================
- Coverage   93.54%   93.42%   -0.12%     
==========================================
  Files          62       61       -1     
  Lines        4400     4260     -140     
  Branches      760      528     -232     
==========================================
- Hits         4116     3980     -136     
+ Misses        282      280       -2     
+ Partials        2        0       -2     

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