don't write no-ops as new URL history items

[taylordowns2000]

Description

This pr closes #4812 by preventing no-ops (where previous URL == new URL) from being added as new URL history items.

Validation steps

1. Go to workflow list
2. Click into workflow
3. Click back
4. See that it works after a single click, not 3 clicks

AI Usage

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• I have used Claude Code
• I have used another model
• I have not used AI

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Pre-submission checklist

• I have performed an AI review of my code (we recommend using /review
  with Claude Code)
• I have implemented and tested all related authorization policies.
  (e.g., :owner, :admin, :editor, :viewer)
• I have updated the changelog.
• I have ticked a box in "AI usage" in this PR

[github-actions]

Security Review ✅

• S0 (project scoping): N/A — change is entirely client-side history.pushState deduplication in assets/js/react/lib/use-url-state.ts:105, no data access.
• S1 (authorization): N/A — no new web-layer actions, controllers, or LiveView events introduced.
• S2 (audit trail): N/A — no config-resource writes; only browser URL/history behavior changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.3%. Comparing base (4e910ec) to head (927c28e).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #4813   +/-   ##
=====================================
  Coverage   90.3%   90.3%           
=====================================
  Files        442     442           
  Lines      22543   22543           
=====================================
+ Hits       20350   20354    +4     
+ Misses      2193    2189    -4     

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