Make the setup-state push report whether it worked

It was documented 'Always returns 0', so the offboard's new 'Phase flags pushed' check was testing a constant and ticking regardless.

Partnership/partnership_onboard.sh

@@ -264,7 +264,12 @@ write_onboard_phase() {
     local state_file="$(platform_setup_db_path)"
     [[ "$DRY_RUN" == true ]] && { warn "DRY RUN — would write ${key}=true"; return 0; }
     set_state_var "$state_file" "$key" "true"
-    platform_push_setup_state
+    # The push now reports failure, so it is warned about rather than returned. This function's
+    # contract is "the phase is recorded here" — the flag is on local disk either way, and an
+    # unreachable partner must not make a completed phase look like it did not happen.
+    platform_push_setup_state \
+        || warn "Phase flag ${key} written locally but not delivered to the partner"
+    return 0
 }