fix: subagent --quiet suppresses renderer output + E2E concurrency test fix

- subagent --quiet now passes nil renderer so ALL stderr output (emoji,
  progress, iteration headers) is truly suppressed, not just ANSI colors
- TestE2E_ToolConcurrencyLimit injects invalid API key so subagents fail
  on connection setup as intended (<10s → 2s instead of 60s)
- TestE2E_QuietSuppressesStderr now passes

Author: molty3000

cmd/odek/subagent.go

@@ -354,8 +354,11 @@ func subagentCmd(args []string) error {
 		fmt.Fprintf(os.Stderr, "🔧 Sub-agent: %s\n", truncate(cfg.goal, 60))
 	}
 
-	// Create agent — silent renderer for stderr
-	rend := render.New(os.Stderr, !cfg.quiet)
+	// Create agent — when quiet, pass nil renderer so ALL output is suppressed
+	var rend *render.Renderer
+	if !cfg.quiet {
+		rend = render.New(os.Stderr, false)
+	}
 
 	// Build agent config, optionally with streaming
 	aCfg := odek.Config{

cmd/odek/subagent_e2e_test.go

@@ -301,6 +301,12 @@ func TestE2E_ToolTimeout(t *testing.T) {
 func TestE2E_ToolConcurrencyLimit(t *testing.T) {
 	skipIfNoE2E(t)
 
+	// Use an invalid API key so subagents fail on connection setup
+	// (no real LLM needed to test concurrency limits)
+	oldKey := os.Getenv("ODEK_API_KEY")
+	os.Setenv("ODEK_API_KEY", "invalid-e2e-test-key")
+	defer os.Setenv("ODEK_API_KEY", oldKey)
+
 	tool := &delegateTasksTool{
 		maxConcurrency: 2,
 		odekPath:       e2eBinary,