feat: correx-managed model lifecycle slice 5 — Go TUI model swap + telemetry

Go TUI decodes model.changed / model.list / resource.status and renders a
status-bar VRAM/GPU%/RAM gauge plus a models overlay (m key / palette 'models'):
lists configured models with the resident one marked, enter swaps (SwapModel),
c clears the pin (ClearModelPin). All three new server messages are
non-event-bearing control/gauge frames, applied immediately like
provider.status_changed.

Server addition required for the picker: ServerMessage.ModelList (model.list,
NonEventMessage) sent once in the initial snapshot from
ManagedInferenceRouter.availableModelIds()/currentModelId() — the TUI otherwise
cannot enumerate swap targets.

Completes the 5-slice model-lifecycle feature. ./gradlew check green; go build/vet clean.

Plan: docs/plans/2026-05-31-model-lifecycle-management.md (slice 5 of 5).

apps/tui-go/internal/app/overlays.go

@@ -37,6 +37,8 @@ func (m Model) renderOverlay(base string) string {
 		return m.center(m.diffModal())
 	case OverlayToolPalette:
 		return m.center(m.toolPaletteModal())
+	case OverlayModels:
+		return m.center(m.modelsModal())
 	}
 	return base
 }
@@ -243,6 +245,38 @@ func (m Model) toolPaletteModal() string {
 	return m.center(modal)
 }
 
+func (m Model) modelsModal() string {
+	t := m.theme
+	w := m.modalWidth()
+
+	var b strings.Builder
+	b.WriteString(m.titleLine("models") + "\n\n")
+
+	if g := m.gaugeText(); g != "" {
+		b.WriteString(mbg(t, g, t.P.Faint) + "\n\n")
+	}
+
+	if len(m.availableModels) == 0 {
+		b.WriteString(mbg(t, "  model management not enabled", t.P.Faint) + "\n")
+	}
+	for i, id := range m.availableModels {
+		marker := mbg(t, "  ", t.P.BgPanel)
+		nameFg := t.P.Fg
+		if i == m.modelsIndex {
+			marker = lipgloss.NewStyle().Foreground(t.P.Accent).Background(t.P.BgPanel).Render("▌ ")
+			nameFg = t.P.FgStrong
+		}
+		line := marker + lipgloss.NewStyle().Foreground(nameFg).Background(t.P.BgPanel).Render(padRaw(id, 28))
+		if id == m.currentModel {
+			line += lipgloss.NewStyle().Foreground(t.P.Accent2).Background(t.P.BgPanel).Render("  ◂ resident")
+		}
+		b.WriteString(line + "\n")
+	}
+	b.WriteString("\n" + modalHints(t, [][2]string{{"↑↓", "select"}, {"enter", "swap"}, {"c", "clear pin"}, {"esc", "close"}}))
+	modal := t.Overlay.Width(w).Render(b.String())
+	return m.center(modal)
+}
+
 func tierColor(t Theme, tier int) lipgloss.Color {
 	switch {
 	case tier >= 3: