fix: Suppress tab-header resize oscillation that causes infinite update loop

[NathanZlion]

When the tabs container is near the overflow threshold, showing/hiding pagination buttons causes a layout shift (~73px) that immediately flips the overflow state back, creating an infinite ResizeObserver loop that eventually triggers React's 'Maximum update depth exceeded' error.

Fix: apply a 2px threshold to the useContainerQuery callback so that sub-pixel or pagination-button-sized width changes are not propagated as new measurements, breaking the oscillation cycle.

Mirrors the pattern used in useContainerWidth (PR #4615).

Fixes AWSUI-62011

Description

Related links, issue #, if available: n/a

How has this been tested?

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

❌ Patch coverage is 75.00000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 97.56%. Comparing base (f968598) to head (4a6d4c3).
⚠️ Report is 32 commits behind head on main.

Files with missing lines	Patch %	Lines
src/tabs/tab-header-bar.tsx	75.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4675      +/-   ##
==========================================
+ Coverage   97.51%   97.56%   +0.05%     
==========================================
  Files         948      948              
  Lines       30346    30492     +146     
  Branches    11067    11151      +84     
==========================================
+ Hits        29593    29751     +158     
+ Misses        706      694      -12     
  Partials       47       47              

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