Add READMEs for: ocaml-fdir, ocaml-initramfs, ocaml-jailhouse,
ocaml-linkedin, ocaml-openamp, ocaml-pid1, ocaml-rpmsg, ocaml-sbom,
ocaml-slack, ocaml-vz, ocaml-zephyr, space, space-block, space-ground,
space-net, space-sim, space-test, space-wire.

Embed a space-net switch inside `space run` so P1 can send telemetry
frames back to the ground station through a dedicated virtio-serial
channel. P1 sends a "boot:complete" TM frame (APID 0x030 -> 0x100)
after storage init, which the switch routes via uplink to ground_flow.

- Rename msg_type type/functions to kind (E330) and drop get_ prefix
from shared_mem getters (E331), updating all callers in space-wire
and space-net
- Add doc comments to all .mli files (E405) and fix superblock doc
style (E410)
- Split monolithic test.ml into per-module test files (E605) and add
.ocamlformat (E500)
- Remove test_space_wire_3d (E610: no corresponding library module)
- Extract helpers from run_guest/run_host in demo.ml to stay under
50-line threshold (E005)

Add documentation to test_config, test_connection, test_router, and
test_switch .mli files. Update Spaceos_wire → Space_wire after package
rename.