fix(federation): allow same-name pinned peer events

[Fail-Safe]

Summary

• Treat pinned peer cortex IDs as remote history in the copied-cortex guard, even when a peer shares the local display name.
• Keep the guard active for unpinned foreign IDs that still indicate reidentified local history.
• Add a regression test for same-name pinned peers.

Checks

• go test ./...
• go vet ./...
• go build ./...