feat: required-binary preflight check in main

Spec error-handling requirement (swaybg/wal always, qarma when GUI).
Caught by final integration review.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/tests/wallp.bats b/tests/wallp.bats
index 0d6fc7e..d7edaec 100644
--- a/tests/wallp.bats
+++ b/tests/wallp.bats
@@ -267,3 +267,16 @@ teardown() {
   main --restore --theme tflag
   [ "$(cat "$HOME/.config/wallp/theme")" = "tflag" ]
 }
+
+@test "missing required binary errors before acting" {
+  unset WAYLAND_DISPLAY
+  rm -f "$STUB_DIR/swaybg"     # swaybg now absent
+  PATH="$STUB_DIR" run main --restore
+  [ "$status" -eq 1 ]
+  [[ "$output" == *"swaybg"* ]]
+}
+
+@test "require_bins passes when all present" {
+  run require_bins
+  [ "$status" -eq 0 ]
+}