Archive guidance

These are frozen, versioned experiments. Keep their dependency pins, distinct purpose, and separate build output. Do not import archived source into the main application or add archive hardware runs to normal CI.

Preserve the original workload when repairing build paths. In particular, the FFT benchmark uses its older Rust radio harness, not the main application's live FFT task. Keep explanatory READMEs focused on reproduction; output belongs in ignored artifacts/archive/.

Build commands must not flash implicitly. Announce any explicit flashing or hardware probe before running it. Preserve the original flash backup, current firmware, and the maintained music pack. Secrets and SDP must stay out of logs shown to the user and out of versioned source.