fix(agent): expose GPT-5.5 family in Codex runtime model picker

Latest Codex CLI ships with GPT-5.5 / GPT-5.5 mini, but the static
catalog still topped out at GPT-5.4 so users couldn't pick the new
model from the agent picker.

Add gpt-5.5 + gpt-5.5-mini to codexStaticModels and promote 5.5 as
the default badge. Keep the older 5.4 / 5.3-codex / gpt-5 / o3
entries for users on older Codex CLI builds. Add a regression test
mirroring TestGeminiStaticModelsExposesAliasesAndGemini3 so the
next OpenAI release isn't a silent miss.

Co-authored-by: multica-agent <github@multica.ai>

server/pkg/agent/models.go

@@ -150,7 +150,9 @@ func claudeStaticModels() []Model {
 
 func codexStaticModels() []Model {
 	return []Model{
-		{ID: "gpt-5.4", Label: "GPT-5.4", Provider: "openai", Default: true},
+		{ID: "gpt-5.5", Label: "GPT-5.5", Provider: "openai", Default: true},
+		{ID: "gpt-5.5-mini", Label: "GPT-5.5 mini", Provider: "openai"},
+		{ID: "gpt-5.4", Label: "GPT-5.4", Provider: "openai"},
 		{ID: "gpt-5.4-mini", Label: "GPT-5.4 mini", Provider: "openai"},
 		{ID: "gpt-5.3-codex", Label: "GPT-5.3 Codex", Provider: "openai"},
 		{ID: "gpt-5", Label: "GPT-5", Provider: "openai"},

server/pkg/agent/models_test.go

@@ -58,6 +58,44 @@ func TestGeminiStaticModelsExposesAliasesAndGemini3(t *testing.T) {
 	}
 }
 
+func TestCodexStaticModelsExposesGPT55(t *testing.T) {
+	// Codex CLI has no `models list` subcommand so the catalog is
+	// hand-maintained. Regression guard for multica-ai/multica#2009 —
+	// GPT-5.5 must be selectable, and the badge default must point at
+	// the latest release rather than lagging a version behind.
+	models := codexStaticModels()
+	ids := map[string]Model{}
+	for _, m := range models {
+		ids[m.ID] = m
+	}
+	for _, want := range []string{
+		"gpt-5.5", "gpt-5.5-mini",
+		"gpt-5.4", "gpt-5.4-mini",
+		"gpt-5.3-codex", "gpt-5",
+		"o3", "o3-mini",
+	} {
+		if _, ok := ids[want]; !ok {
+			t.Errorf("missing expected Codex model %q in: %+v", want, models)
+		}
+	}
+	latest, ok := ids["gpt-5.5"]
+	if !ok || !latest.Default {
+		t.Errorf("expected `gpt-5.5` to be the default Codex entry, got %+v", latest)
+	}
+	defaults := 0
+	for _, m := range models {
+		if m.Default {
+			defaults++
+		}
+		if m.Provider != "openai" {
+			t.Errorf("all Codex entries must carry Provider=openai, got %+v", m)
+		}
+	}
+	if defaults != 1 {
+		t.Errorf("expected exactly one default Codex entry, got %d", defaults)
+	}
+}
+
 func TestListModelsHermesWithoutBinary(t *testing.T) {
 	// With no `hermes` binary on PATH the discovery fast-paths to
 	// an empty list (the UI then falls back to creatable manual