Adds the official 3.1.7 spec JSON set alongside the sealed 3.1.6 set.
Pure additive (+1 Mode OFDM, +4 Submodes FT2/FREEDATA/RIBBIT_PIX/RIBBIT_SMS).
Also restores resources/schemas/manifest.v1.json to unblock the
validate-manifest CI step (broken on main since 7bde757).