Implement identical-links-same-context rule (fd3a94)

[koddsson]

ACT Rule

• ACT Rule ID: fd3a94
• Rule Name: Links with identical accessible names and same context serve equivalent purpose
• WCAG SC: 2.4.4 Link Purpose (In Context) (Level A)

What it checks

This rule checks that links with identical accessible names that are in the same context point to equivalent resources.

Feasibility

DOM-only feasible. Involves finding links with the same accessible name, grouping by context, and checking if href attributes point to equivalent resources.

Notes

• Related to issue 35 W3C ACT rules have no corresponding scanner rule #350 (ACT rules triage)
• The existing identical-links-same-purpose scanner rule (mapped to ACT rule b20e66) covers links regardless of context; this is the same-context variant
• May be able to extend the existing rule implementation

[koddsson]

After reviewing the ACT test cases, this rule requires determining if different URLs serve equivalent content (e.g., redirect URLs, URL copies). Several "passed" test cases have links with different href values that are semantically equivalent — a DOM-only scanner cannot determine this without fetching the URLs. The "failed" cases (different domains, different query params) could be caught with a heuristic, but the false positive rate from "passed" cases would be high. Marking as complex/out-of-scope for now.