Explicit host config outranks the local build-host inference; document it

The published-db marker also exists on any workstation that once ran a full
local release, so --host / OMARCHY_REPO_HOST / .repo-host are now checked
before on_repo_host everywhere (triggers, advances, doctor). README documents
the detection, the caveat, and the .repo-host tie-breaker.

bin/omarchy-pkgs

@@ -323,7 +323,9 @@ regenerate_checksums() {
 
 trigger_build_host() {
   local host
-  if on_repo_host; then
+  # Explicit host configuration outranks the local-host inference (a
+  # workstation that ran a full local release carries the db marker too).
+  if ! resolve_repo_host "${REPO_HOST_OVERRIDE:-}" >/dev/null && on_repo_host; then
     print_info "Triggering edge build locally (this is the build host)..."
     if mkdir -p "${OMARCHY_STATE_DIR:-/root/.state}" &&
       touch "${OMARCHY_STATE_DIR:-/root/.state}/.sync-needed-edge" &&