fed-sx-m1: Step 1b — nx_cid kernel module + 13 canonical CID tests

next/kernel/nx_cid.erl

@@ -0,0 +1,24 @@
+-module(nx_cid).
+-export([from_sx/1, to_string/1, from_string/1, equals/2]).
+
+%% The kernel-side CID wrapper. The host BIF `cid:to_string/1` already
+%% produces a canonical CIDv1 (raw codec, sha2-256 multihash) over the
+%% deterministic textual form of any term (er-format-value); we expose
+%% it under the kernel namespace and add the equality + round-trip
+%% helpers the rest of the kernel needs.
+%%
+%% Naming note: the BIF module is `cid`, so we use `nx_cid` to avoid
+%% shadowing. Plans/fed-sx-milestone-1.md §Step 1 spells the file as
+%% `cid.erl`; the briefing flags Erlang snippets as illustrative.
+
+from_sx(V) ->
+    cid:to_string(V).
+
+to_string(Cid) ->
+    Cid.
+
+from_string(S) ->
+    S.
+
+equals(A, B) ->
+    A =:= B.