proximity1, space-wire: add c/ scaffold for EverParse 3D codegen
Both packages use Wire.Codec but had no c/ subdirectory, so merlint's
global check flagged them as missing the EverParse 3D entry point.
Add a minimal c/ for each: gen.ml that calls Wire_3d.main on the
codec(s), a dune file with the standard (alias gen) layout, and an
empty dune.inc placeholder. Running `dune build @<pkg>/c/gen` regenerates
dune.inc + the .3d, .h, .c, etc. when the EverParse 3D toolchain is on
PATH.
For proximity1 the codec is the single Proximity1.codec; for space-wire
we generate one .3d per Wire.Everparse.module_ defined in
space-wire/lib/wire/space_wire_3d.ml (frame, error/dp payload,
superblock, parameter entry, event log).