[mugiwarafx]

Summary

An image with a non-empty alt and role="presentation" currently contributes a name to its containing heading because getResolvedRole filters explicit roles through the host element's author-conformance allowlist. Both heading checks therefore pass ACT ffd0e9 Failed Example 4, which expects failure:

<h1><img alt="ACT rules" role="presentation"></h1>

Resolve the first supported explicit role independently of author validation, retaining presentational-role conflict handling for focusability (including negative tabindex) and global ARIA attributes. getInvalidRoles continues to validate author conformance against the existing tables. Explicit-only lookups use a separate cache entry to prevent implicit-role results from leaking between lookup modes.

This shared-resolver change also restores two missing-parent failures in an existing fixture (treeitem and menuitem roles on disallowed hosts). Regression tests cover the heading example, role precedence, focus/global-attribute exceptions, and cache order. The draft leaves ACT mapping and the remaining ffd0e9 discrepancies for follow-up, and requests review of the resolver behavior in the context of #2629's IBM guidance alignment requirement.

• New or modified checker rule(s)
• New or modified help files
• Simulator updates
• Extension UI changes
• Automated tool changes
• Other (Shared engine utility and regression tests)

This PR is related to the following issue(s):

• Related to Epic: ACT Rules Consistency Alignment (2025) #2629 (ffd0e9 presentational-image discrepancy).

Testing reference:

• npm run build-debug: passed.
• npm test: 1,641 passed (1,619 existing tests plus 22 new regression tests).
• npm run test:sr -- --port 9878: 332 passed.
• Compared the same 15 ffd0e9 fixtures before and after the change: only Failed Example 4 changes, from passed to failed in both candidate rules. This was a local engine probe, not the full ACT driver.
• git diff --check: passed. Local validation used Node v24.16.0 and Chrome 155 on macOS.

I have conducted the following for this PR:

• I validated this fix in my local env and provided testing information above
• I understand that the title of this PR will be used for the next release notes.
• I added I agree to the DCO at https://developercertificate.org/ for this contribution. as a comment after creating the pull request.

Assets to aide review attached

• Links to design artifacts
• Links to video walkthrough of user experience
• Other

Definition of Done

• Peer review complete
• Secondary review complete
• Staging deployment verified