feat(ui): migrar a tokens + primitivos del design system

Dashboard ahora usa:
- fn_tokens::apply_dark_theme() al primer frame (colors + spacing
  + radius + rounding consistentes con @fn_library / Mantine).
- page_header_begin/end para el header (en vez de Text + Separator
  + Button manual). Subtítulo con conteos de entidades.
- empty_state en las 4 tablas cuando están vacías — mensaje amable
  con acción sugerida en lugar de tabla vacía silenciosa.

Nuevas deps de compilación (.cpp fuentes añadidas al CMakeLists):
tokens.cpp, badge.cpp, empty_state.cpp, page_header.cpp.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

views.cpp

@@ -11,7 +11,12 @@
 #include "core/dashboard_grid.h"
 #include "core/fps_overlay.h"
 #include "core/fullscreen_window.h"
+#include "core/tokens.h"
+#include "core/page_header.h"
+#include "core/empty_state.h"
+#include "core/badge.h"
 
+#include <cstdio>
 #include <vector>
 
 static std::vector<const char*> to_cstr(const std::vector<std::string>& v) {
@@ -87,6 +92,11 @@ void draw_charts(RegistryData& data, float height) {
 }
 
 void draw_recent_functions(const std::vector<FunctionRow>& funcs) {
+    if (funcs.empty()) {
+        empty_state("( no data )", "No functions yet",
+                    "Run 'fn index' to populate the registry");
+        return;
+    }
     const char* headers[] = {"Name", "Lang", "Domain", "Kind", "Purity", "Tested", "Created"};
     constexpr int cols = 7;
     std::vector<std::string> cell_strings;
@@ -105,6 +115,11 @@ void draw_recent_functions(const std::vector<FunctionRow>& funcs) {
 }
 
 void draw_apps_list(const std::vector<AppRow>& apps) {
+    if (apps.empty()) {
+        empty_state("( no data )", "No apps registered",
+                    "Clone apps with 'fn app clone <id>' or run 'fn sync'");
+        return;
+    }
     const char* headers[] = {"Name", "Lang", "Domain", "Framework", "Description"};
     constexpr int cols = 5;
     std::vector<std::string> cell_strings;
@@ -121,6 +136,11 @@ void draw_apps_list(const std::vector<AppRow>& apps) {
 }
 
 void draw_analysis_list(const std::vector<AnalysisRow>& analyses) {
+    if (analyses.empty()) {
+        empty_state("( no data )", "No analysis yet",
+                    "Create one with 'fn run init_jupyter_analysis <name>'");
+        return;
+    }
     const char* headers[] = {"Name", "Domain", "Description"};
     constexpr int cols = 3;
     std::vector<std::string> cell_strings;
@@ -135,6 +155,11 @@ void draw_analysis_list(const std::vector<AnalysisRow>& analyses) {
 }
 
 void draw_types_list(const std::vector<TypeRow>& types) {
+    if (types.empty()) {
+        empty_state("( no data )", "No types yet",
+                    "Types are indexed from the registry alongside functions");
+        return;
+    }
     const char* headers[] = {"Name", "Lang", "Domain", "Algebraic", "Description"};
     constexpr int cols = 5;
     std::vector<std::string> cell_strings;
@@ -151,31 +176,44 @@ void draw_types_list(const std::vector<TypeRow>& types) {
 }
 
 void draw_dashboard(RegistryData& data) {
+    // Aplicar tema una sola vez por vida de la app.
+    static bool theme_applied = false;
+    if (!theme_applied) {
+        fn_tokens::apply_dark_theme();
+        theme_applied = true;
+    }
+
     fps_overlay();
     fullscreen_window_begin("##dashboard");
 
-    float win_h = ImGui::GetContentRegionAvail().y;
+    // Subtitle con conteos — contexto rápido para el usuario
+    char subtitle[128];
+    std::snprintf(subtitle, sizeof(subtitle),
+        "%d functions  ·  %d types  ·  %d apps  ·  %d analyses",
+        data.stats.total_functions, data.stats.total_types,
+        data.stats.total_apps, data.stats.total_analysis);
 
-    // Row 1: Header + KPIs (~80px)
-    ImGui::Text("fn_registry Dashboard");
-    ImGui::SameLine(ImGui::GetWindowWidth() - 100);
+    // Header con acción Reload a la derecha
+    page_header_begin("fn_registry Dashboard", subtitle);
+    ImGui::SameLine(ImGui::GetWindowWidth() - 120.0f);
     if (ImGui::Button("Reload")) {
         ImGui::GetIO().UserData = reinterpret_cast<void*>(1);
     }
-    ImGui::Separator();
+    page_header_end();
 
+    // KPIs
     draw_kpi_row(data.stats);
-    ImGui::Separator();
+    ImGui::Dummy(ImVec2(0, fn_tokens::spacing::md));
 
-    // Row 2: Charts — take 35% of remaining height
+    // Charts — 35% de la altura restante
     float remaining = ImGui::GetContentRegionAvail().y;
     float chart_h = remaining * 0.35f;
     if (chart_h < 150.0f) chart_h = 150.0f;
 
     draw_charts(data, chart_h);
-    ImGui::Separator();
+    ImGui::Dummy(ImVec2(0, fn_tokens::spacing::md));
 
-    // Row 3: Tables — fill the rest
+    // Tables
     if (ImGui::BeginTabBar("##tables")) {
         if (ImGui::BeginTabItem("Recent Functions")) {
             draw_recent_functions(data.recent_funcs);