The initial selective strip covered only the Authorization header, but the
dashboard also accepts its JWT via the ?token= query parameter and the
nz-jwt cookie (jwt.go TokenLookup channels). A dashboard credential arriving
through those channels would still reach a NAT backend.
Apply the same classify-then-strip rule to all three channels at NAT
ingress: values verified as dashboard-issued are removed, foreign values
are preserved byte-for-byte. Adds a ServeNAT flow test exercising the live
classifier and a wiring test pinning the gate injection in main().
naiba
xvkong233