On the flaky NG link a command's response can arrive *after* its read times out, and the
next command's read then picks up that stale frame — observed in rawcli as every raw 14a
command returning "04 BB" (the truncated UID from _ensure_selected's timed-out scan) instead
of its own response.
read_response/_read_any_response now set a _resync_needed flag on timeout, and the next
send_frame drains any late/stale input before writing. Cheap — only fires after a timeout
(rare on a healthy link) and no-ops when the stream is clean. Hardware-verified: identify ->
NTAG216, READ(4) 6/6 correct, GET_VERSION correct, with the hardening in place.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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