5.2.1 is a quality pass on the stream-aware 5.2.0 release — no new tools, just tighter, less noisy suggestions.

• Target suggestions are filtered to the support-matrix selectable set, so the server only offers targets a user can actually build for, and a short two-character overlap no longer conflates architectures (x86_64 no longer pulls in qemuarm64), with a regression test locking the guard in place.
• Resolver noise, tmux session addressing in the device-info snippet, and duplicate validators are cleaned up from review follow-ups on the 5.2.0 work.