New unit tests for singleCellCellType & singleCellGeneExpression tws

[creilly8]

Description

Not urgent. Started new unit test files for tw/singleCellCellType.ts and tw/singleCellGeneExpression.ts

Supports efforts detailed in SC roadmap

Checklist

Check each task that has been performed or verified to be not applicable.

• Tests: Added and/or passed unit and integration tests, or N/A
• Todos: Commented or documented, or N/A
• Notable Changes: updated release.txt, prefixed a commit message with "fix:" or "feat:", added to an internal tracking document, or N/A
• Rust: Checked to see whether Rust needs to be re-compiled because of this PR, or N/A

[Copilot]

Pull request overview

Adds initial unit test coverage for the new single-cell termwrapper implementations and aligns termwrapper term.type constants with the shared TermTypes enum-like map.

Changes:

• Added new unit test specs for tw/singleCellCellType and tw/singleCellGeneExpression.
• Updated single-cell termwrapper modules to use TermTypes.* instead of hardcoded strings.
• Tightened singleCellGeneExpression validation to handle null terms.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
release.txt	Notes the addition of unit tests in the release log.
client/tw/test/singleCellGeneExpression.unit.spec.ts	Adds unit tests for getSCGEunit(), validate(), fill(), and constructor behavior.
client/tw/test/singleCellCellType.unit.spec.ts	Adds unit tests for validate(), fill(), and constructor defaults.
client/tw/singleCellGeneExpression.ts	Switches to TermTypes.SINGLECELL_GENE_EXPRESSION and improves null checking in validate().
client/tw/singleCellCellType.ts	Switches to a TermTypes constant for termType (but currently uses a non-existent key).

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[Copilot]

TermTypes does not define SINGLECELL_CELL_TYPE (the existing constant is TermTypes.SINGLECELL_CELLTYPE: 'singleCellCellType'). As written, termType will be undefined, which breaks validation/type checks and can let invalid terms pass silently. Update this to use the correct TermTypes key so termType resolves to 'singleCellCellType'.

Suggested change

	const termType = TermTypes.SINGLECELL_CELL_TYPE
	const termType = TermTypes.SINGLECELL_CELLTYPE

[Copilot]

Tests are using TermTypes.SINGLECELL_CELL_TYPE, but TermTypes defines SINGLECELL_CELLTYPE (no _TYPE). Using the non-existent key makes term.type undefined, which can cause these tests to pass even while the implementation is broken. Replace all occurrences with TermTypes.SINGLECELL_CELLTYPE and consider asserting the expected type string in the thrown error message to prevent this class of regression.

Suggested change

	type: TermTypes.SINGLECELL_CELL_TYPE,
	type: TermTypes.SINGLECELL_CELLTYPE,