tests: move the test-only constructors into export_test.go (closes #111)

state.NewForTest, state.NewForTestWithDataDir and watcher.NewForTest
were compiled into and exported by the production packages
internal/state and internal/watcher. NewForTestWithDataDir and
watcher.NewForTest now live in their package's export_test.go. Tests in
other packages cannot see those files, so the watcher and middleware
tests build their State with state.New and a temporary data directory;
the watcher tests no longer try to save to /state.json.
state.NewForTest, whose State saved to /, is deleted: the state tests
that used it pass t.TempDir() to NewForTestWithDataDir, and the test of
the helper itself is gone.

Model: opus-5-5

internal/watcher/watcher.go

@@ -102,28 +102,6 @@ func New(
 	return w, nil
 }
 
-// NewForTest creates a Watcher without fx for unit testing.
-func NewForTest(
-	cfg *config.Config,
-	st *state.State,
-	res DNSResolver,
-	pc PortChecker,
-	tc TLSChecker,
-	n Notifier,
-) *Watcher {
-	return &Watcher{
-		log:            slog.Default(),
-		config:         cfg,
-		state:          st,
-		resolver:       res,
-		portCheck:      pc,
-		tlsCheck:       tc,
-		notify:         n,
-		firstRun:       true,
-		expiryNotified: make(map[string]time.Time),
-	}
-}
-
 // Run starts the monitoring loop with periodic scheduling.
 func (w *Watcher) Run(ctx context.Context) {
 	w.log.Info(