[12] [C#-CORE.GUID] guid.rs HasEntry always-true; verify per GUID type vs C++

[alseif0x]

crates/wow-core/src/guid.rs:329 HasEntry returns true unconditionally (from C#). C++ ObjectGuid has entry only for certain high-GUID types.
C++: ObjectGuid / ObjectGuidFactory (HasEntry semantics by type).

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From the C#-vs-C++ reference audit (local docs/audits/csharp-reference-contrast.md). Plan: docs/migration/PORT_PLAN.md (L26) · State: docs/migration/STATE.md.
Done = contrast Rust vs the cited C++; if it matches, re-anchor the comment to C++ file:line; if it differs, fix behavior to C++. Live + capture-clean. 1 issue = 1 PR.