Fix failing structured trace handler reuse test on master

[MySweetEden]

Summary
Fix test_structured_optimization_trace_reuses_handler_for_repeated_contexts, which is currently failing on master.

On the Windows runner, the one-second time limit could be exhausted during presolving, before any trace event was emitted. This left the trace with only a run_end record and caused the test to fail.

This PR:

• disables presolving in the structured trace handler reuse test
• retains the five-second optimization limit configured by _model()

Why this was not caught before merge
The failure was detected only after merging because the Integration test workflow runs on pushes to master, but not on pull requests.

Follow-up
I propose tracking the pre-merge CI coverage gap in a separate issue, including whether the Integration test workflow should run before merge. This PR leaves the CI configuration unchanged and is limited to fixing the failing test.

[Joao-Dionisio]

Hey @MySweetEden , thank you!

I propose tracking the pre-merge CI coverage gap in a separate issue, including whether the Integration test workflow should run before merge.

On this, it's a good idea. One requirement would be that it doesn't run every push, to avoid wasting resources, but only at merge time.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 57.27%. Comparing base (9547994) to head (054b47f).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1246      +/-   ##
==========================================
- Coverage   57.91%   57.27%   -0.64%     
==========================================
  Files          26       27       +1     
  Lines        5807     5915     +108     
==========================================
+ Hits         3363     3388      +25     
- Misses       2444     2527      +83     

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