Fix user bubble text contrast, Chat nav active state, and update summary.md

- theme.css: darken user bubble text (#3a3a4a light / #b0b0c8 dark) for better readability
- AppHeader: highlight Chat nav link when on any /chat/* route (was only active on exact /chat)
- summary.md: document workspace, graph, queue persistence, ToolCallCard direct-API, dedup scoping

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/components/AppHeader.vue

@@ -1,6 +1,6 @@
 <script setup lang="ts">
 import { ref, computed, onMounted, onUnmounted } from "vue";
-import { useRouter } from "vue-router";
+import { useRouter, useRoute } from "vue-router";
 import { useTheme } from "@/composables/useTheme";
 import { useShortcuts } from "@/composables/useShortcuts";
 import { useAuthStore } from "@/stores/auth";
@@ -12,6 +12,9 @@ const { toggleShortcuts } = useShortcuts();
 const authStore = useAuthStore();
 const chatStore = useChatStore();
 const router = useRouter();
+const route = useRoute();
+
+const isChatActive = computed(() => route.path.startsWith("/chat"));
 
 const mobileMenuOpen = ref(false);
 const gearOpen = ref(false);
@@ -87,7 +90,7 @@ onUnmounted(() => document.removeEventListener("click", handleClickOutside));
         <router-link to="/notes" class="nav-link">Notes</router-link>
         <router-link to="/projects" class="nav-link">Projects</router-link>
         <router-link to="/tasks" class="nav-link">Tasks</router-link>
-        <router-link to="/chat" class="nav-link">Chat</router-link>
+        <router-link to="/chat" :class="['nav-link', { 'router-link-active': isChatActive }]">Chat</router-link>
         <router-link to="/graph" class="nav-link">Graph</router-link>
       </div>
 
@@ -139,7 +142,7 @@ onUnmounted(() => document.removeEventListener("click", handleClickOutside));
       <router-link to="/notes" class="nav-link">Notes</router-link>
       <router-link to="/projects" class="nav-link">Projects</router-link>
       <router-link to="/tasks" class="nav-link">Tasks</router-link>
-      <router-link to="/chat" class="nav-link">Chat</router-link>
+      <router-link to="/chat" :class="['nav-link', { 'router-link-active': isChatActive }]">Chat</router-link>
       <router-link to="/graph" class="nav-link">Graph</router-link>
       <div class="mobile-divider"></div>
       <router-link to="/settings" class="nav-link">Settings</router-link>