fix: start epmd before net_kernel in split_dc_SUITE; ci: epmd -daemon

split_dc_SUITE requires Erlang distribution (peer module). On GitHub
Actions (and any fresh environment) epmd is not pre-started, causing
net_kernel:start to fail with nodistribution.

Fix: call os:cmd("epmd -daemon") before net_kernel:start in
init_per_suite. The call is idempotent — safe when epmd is already
running.

Also start epmd explicitly in the CI 'ct' step as a belt-and-suspenders
measure.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: seriyps

.github/workflows/ci.yml

@@ -45,7 +45,7 @@ jobs:
         run: rebar3 eunit
 
       - name: ct
-        run: rebar3 ct
+        run: epmd -daemon && rebar3 ct
 
       - name: dialyzer
         run: rebar3 dialyzer

test/split_dc_SUITE.erl

@@ -38,7 +38,9 @@ init_per_suite(Cfg) ->
     {ok, _} = application:ensure_all_started(inets),
     {ok, _} = application:ensure_all_started(ranch),
     %% peer:start_link requires the current node to be distributed.
-    %% Start distribution if rebar3 ct didn't already do so.
+    %% Start EPMD daemon first (no-op if already running), then enable
+    %% distribution if rebar3 ct didn't already do so.
+    os:cmd("epmd -daemon"),
     Distributed =
         case net_kernel:start([split_dc_test, shortnames]) of
             {ok, _}                       -> true;