JS: Improve useless-expression query to avoid duplicate alerts on compound expressions

[Napalys]

This PR improves the js/useless-expression query by adding logic to avoid flagging compound expressions that may contain sub-expressions with side effects.

[Copilot]

Pull Request Overview

Enhance the isDomProperty predicate to detect property reads on DOM nodes (e.g., offsetHeight, clientWidth) and reduce false positives in the js/useless-expression query.

• Extend isDomProperty to also match property names accessed via data-flow property reads.
• Add a test case validating layout-affecting reads on DOM elements.
• Record the change in the project’s change notes.

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
javascript/ql/lib/Expressions/DOMProperties.qll	Extend isDomProperty predicate with a DataFlow::SourceNode branch.
javascript/ql/test/query-tests/Expressions/ExprHasNoEffect/dom.js	New test verifying that reads like offsetHeight and clientWidth are side-effectful.
javascript/ql/lib/change-notes/2025-05-26-dom-property-access.md	Add change note documenting the enhancement to isDomProperty.

Comments suppressed due to low confidence (1)

javascript/ql/lib/Expressions/DOMProperties.qll:14

• [nitpick] The variable name domNode implies a DOM AST node but actually refers to a data-flow source; consider renaming it to sourceNode or propSourceNode for clearer intent.

exists(DataFlow::SourceNode domNode | isDomNode(domNode) |