perf: improve runtime performance of exhaustive search

[triceo]

No description provided.

[Copilot]

Pull request overview

This PR optimizes exhaustive search runtime by reducing per-step allocations and stream overhead, and by simplifying several hot-path code paths involved in node expansion, undo handling, and destination selection.

Changes:

• Replace stream-based iteration in list destination selection with lightweight iterator implementations (MappingIterator, ConcatenatingIterator).
• Reduce allocation/copying on the undo hot path by returning an undo Move from the recording score director and resetting the internal change list by reference swap.
• Micro-optimize exhaustive search internals (comparators, queue operations, remove unused expandable tracking).

Reviewed changes

Copilot reviewed 15 out of 15 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
core/src/main/java/ai/timefold/solver/core/impl/score/director/RevertableScoreDirector.java	Replaces copyChanges() with createUndoMove() and updates contract/Javadoc.
core/src/main/java/ai/timefold/solver/core/impl/move/VariableChangeRecordingScoreDirector.java	Implements createUndoMove() without copying and swaps the change list on undo.
core/src/main/java/ai/timefold/solver/core/impl/move/EphemeralMoveDirector.java	Switches to the new createUndoMove() API.
core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/list/ElementDestinationSelector.java	Removes stream usage in iterators and switches to new iterator utilities.
core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/common/iterator/MappingIterator.java	Adds a minimal mapping iterator to avoid stream overhead.
core/src/main/java/ai/timefold/solver/core/impl/heuristic/selector/common/iterator/ConcatenatingIterator.java	Adds a concatenating iterator to avoid stream concatenation overhead.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/scope/ExhaustiveSearchPhaseScope.java	Removes unused depth/expandable tracking and simplifies expandable node addition.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/comparator/ScoreFirstNodeComparator.java	Simplifies comparator logic to reduce branching.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/comparator/OriginalOrderNodeComparator.java	Simplifies comparator logic to reduce branching.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/comparator/OptimisticBoundFirstNodeComparator.java	Simplifies comparator logic to reduce branching.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/comparator/DepthFirstNodeComparator.java	Simplifies comparator logic to reduce branching.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/comparator/BreadthFirstNodeComparator.java	Simplifies comparator logic to reduce branching.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/node/ExhaustiveSearchNode.java	Removes unused expandable field/accessors.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/decider/AbstractExhaustiveSearchDecider.java	Removes expandable logging and uses getFirst() for layer access.
core/src/main/java/ai/timefold/solver/core/impl/exhaustivesearch/DefaultExhaustiveSearchPhase.java	Uses removeLast() to pop the next node more directly.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
91.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud