test: run the config-settings render golden in the test runner

A byte-identity gate CI never runs will rot, and a rotted gate is worse
than no gate. Adds the render harness as Phase 4, in the same shape as the
vault suite: its own process, its own sandbox, no loaded config needed.

Kept to one self-contained block so it can be dropped or re-applied by
hand if the runner is restructured. The functional suite's 317/317 count
is untouched; the render cases report separately.

tests/run-tests.fish

@@ -100,4 +100,15 @@ if test $status -ne 0
     set overall_failed 1
 end
 
+# ---- Phase 4: config-settings render golden ------------------------------
+# Byte-identity gate for the TUI's three draw functions. Runs as its own
+# process: like the vault suite it builds its own throwaway
+# HOME/XDG_CONFIG_HOME sandbox and needs no loaded config.
+echo ""
+echo "== config-settings render golden =="
+fish $repo_root/tests/config-settings-render.fish
+if test $status -ne 0
+    set overall_failed 1
+end
+
 exit $overall_failed