16 write work model tests

[lifflander]

Closes #16

[lifflander]

More test need to be written

[Copilot]

Pull request overview

This PR adds unit tests for the work model functionality in the load balancing library and introduces a simplified Task constructor to facilitate test creation.

• Adds comprehensive unit tests for WorkModelCalculator functionality including work computation, memory usage, and incremental updates
• Introduces a simplified Task(TaskType id, LoadType load) constructor for easier task creation in tests

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
tests/unit/work_model/test_work_model.cc	New test file with 4 test cases covering work computation, memory usage calculation, memory fit checking, and work update operations
src/vt-lb/model/Task.h	Adds simplified two-parameter constructor for creating Task instances with just ID and load

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[Copilot]

[nitpick] Consider adding documentation for this constructor to clarify its intended use case and the default values that will be used for uninitialized fields (home_, current_, migratable_, memory_, shared_blocks_). This would help other developers understand when to use this simplified constructor versus the full constructor.

Suggested change

	Task() = default;
	Task() = default;
	/**
	* @brief Simplified constructor for Task.
	*
	* Initializes a Task with the given id and load.
	* Other fields are set to their default values:
	* - home_ = invalid_node
	* - current_ = invalid_node
	* - migratable_ = true
	* - memory_ = default-constructed TaskMemory (all fields 0.0)
	* - shared_blocks_ = empty set
	*
	* Use this constructor when only id and load are known, and other fields can be defaulted.
	* For full control, use the more detailed constructor.
	*/