v0.285.0 — a box keeps two controller versions (decision 56, R-745); the update clean-up's nil-stack crash (R-751)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/stacks/r650_main_test.go

@@ -9,4 +9,13 @@ import (
 
 // TestMain puts a silent docker stub on PATH for every test in this package: R-650, the fixtures
 // here build a real stacks.Manager, and on the build host (DooPlex) that reached production Docker.
-func TestMain(m *testing.M) { os.Exit(dockerexec.RunWithStub(m)) }
+//
+// R-751: the retention after an update or a remove runs in a GOROUTINE that outlives the test that triggered it — it
+// wrote into a test's temp dir while the dir was being removed ("directory not empty") and once panicked on the
+// vanished stack. No test here may leave one running: both seams are no-ops by default; the retention tests call
+// RetainImagesAfter* directly, and the wiring tests swap the seams themselves.
+func TestMain(m *testing.M) {
+	retainAfterUpdateFn = func(*Manager, string, map[string]InstalledImage) {}
+	retainAfterRemoveFn = func(*Manager, string, map[string]bool) {}
+	os.Exit(dockerexec.RunWithStub(m))
+}