LDEV-6309: failing spec for self-referential struct inspection

[zspitzer]

Summary

• Failing TestBox spec reproducing LDEV-6309
• StackOverflowError when expanding the variables scope on a struct that references itself

Test only — no fix yet. Pushing this first to watch CI go red, then a follow-up commit will apply the fix in ValTracker.java.

Reported on dev.lucee.org: https://dev.lucee.org/t/lucee-debugger-extension-in-vscode/17236/5

Repro

s = {};
s.self = s;
// breakpoint here, expand `variables` in VS Code -> StackOverflowError

Stack trace cycles between StructImpl.hashCode() and ConcurrentHashMapNullSupportJDK.hashCode().

Root cause (for the follow-up fix)

ValTracker.wrapperByObj is a WeakHashMap — keys compared by equals()/hashCode() rather than identity. Every idempotentRegisterObject(obj) calls hashCode() on the value. Self-referential struct → infinite recursion.

Fix in follow-up: swap to org.lucee.extension.debugger.util.ConcurrentWeakKeyMap (already in the project, identity-keyed via System.identityHashCode).

Test plan

• CI fails on the new it() block in VariablesTest.cfc with StackOverflowError
• Existing variables tests still pass (new artifact is isolated)
• Follow-up fix commit turns CI green