Add unit tests for QueryTrait

[WarLikeLaux]

Q	A
Is bugfix?	❌
New feature?	❌
Breaks BC?	❌
Fixed issues

What does this PR do?

Adds isolated unit tests for QueryTrait methods via Query without database connection.

Before

No dedicated unit test for QueryTrait.
Existing QueryTest extends DatabaseTestCase and requires DB connection.

After

Tests: 96, Assertions: 111
Methods: 73% (11/15), Lines: 86% (70/81)
MSI: 91% (101/111 mutants killed)

4 methods and 11 lines uncovered - QueryTrait::where(), andWhere(), orWhere() trait versions are not executed because Query overrides them with parameter binding support. Line 235 is a defensive guard (!is_array) unreachable through filterWhere() which type-hints array.

Escaped mutants (all equivalent)

QueryTrait.php (10): ProtectedVisibility ×3 - L232, L302, L365, protected → private always equivalent. IncrementInteger - L238, condition[0] → condition[1]: hash format never has numeric keys, operator format always has both. DecrementInteger ×3 - L272, L272, L279, array_key_exists(1,...) → array_key_exists(0,...): after array_shift, keys 0-2 always exist in well-formed conditions. IncrementInteger - L272, same reason. LogicalAnd - L272, && → ||: both keys always present, guard is defensive. PregMatchRemoveCaret - L378, ^ redundant with non-greedy (.*?) at start.

Changelog not required, because no source files changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.13%. Comparing base (37b6e7b) to head (331dd72).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff            @@
##             master   #20773   +/-   ##
=========================================
  Coverage     80.13%   80.13%           
  Complexity    11533    11533           
=========================================
  Files           374      374           
  Lines         30206    30206           
=========================================
  Hits          24207    24207           
  Misses         5999     5999           

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