`user does not exist [uid: 0, name: ]` from tea reads as a missing account.
It almost always means a revoked or stale token: `tea login` keeps its own
copy of the token, so rotating the credential store does not update it. The
error points at the account; the cause is the cached credential.
Adds explain_tea_user_does_not_exist() to detect-platform.sh and invokes it
from the three tea-failure fallback paths, each guarded by `declare -F` so
the call site is independent of load order and a no-op if the helper is absent.
Purely additive: stderr only, no control flow, no gate or credential changes.
Verified both directions: the helper emits when sourced, and the guarded call
is a silent no-op (exit 1, no output) when it is not.
Refs #1082
Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01Amf1Neca162odgcbCWMk1y
