feat(app): add error boundaries and fix ESLint config for Vue+TS

- Wrap ChatMessage v-for loop in ChatWindow with ErrorBoundary
- Wrap ContentPanel grid/detail sections with ErrorBoundary
- Fix ESLint flat config: add vue-eslint-parser for TypeScript in SFCs
- Add browser globals to ESLint config
- Fix lint errors in contentExtraction.ts (useless escapes, prefer-const,
  unicode flag for emoji regex)

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

packages/app/src/components/ui/ErrorBoundary.vue

@@ -0,0 +1,88 @@
+<template>
+  <slot v-if="!error" />
+  <div
+    v-else
+    class="flex items-center justify-center p-4"
+    role="alert"
+  >
+    <div
+      class="rounded-xl p-4 max-w-sm w-full space-y-3"
+      :class="isDark
+        ? 'bg-red-500/10 border border-red-500/20'
+        : 'bg-red-50 border border-red-200'"
+    >
+      <div class="flex items-start gap-3">
+        <svg
+          class="w-5 h-5 text-red-500 shrink-0 mt-0.5"
+          fill="none"
+          stroke="currentColor"
+          viewBox="0 0 24 24"
+          aria-hidden="true"
+        >
+          <path
+            stroke-linecap="round"
+            stroke-linejoin="round"
+            stroke-width="2"
+            d="M12 9v2m0 4h.01m-6.938 4h13.856c1.54 0 2.502-1.667 1.732-2.5L13.732 4.5c-.77-.833-2.694-.833-3.464 0L3.34 16.5c-.77.833.192 2.5 1.732 2.5z"
+          />
+        </svg>
+        <div class="min-w-0">
+          <h3
+            class="text-sm font-semibold"
+            :class="isDark ? 'text-red-400' : 'text-red-900'"
+          >
+            {{ title }}
+          </h3>
+          <p
+            v-if="errorMessage"
+            class="text-xs mt-1 break-words"
+            :class="isDark ? 'text-red-300/70' : 'text-red-700/70'"
+          >
+            {{ errorMessage }}
+          </p>
+        </div>
+      </div>
+      <button
+        class="text-xs px-3 py-1.5 rounded-lg transition-colors"
+        :class="isDark
+          ? 'text-red-300 hover:bg-red-500/20'
+          : 'text-red-600 hover:bg-red-100'"
+        @click="reset"
+      >
+        Try again
+      </button>
+    </div>
+  </div>
+</template>
+
+<script setup lang="ts">
+import { ref, onErrorCaptured } from 'vue'
+import { useTheme } from '@/composables/useTheme'
+
+withDefaults(
+  defineProps<{
+    title?: string
+  }>(),
+  {
+    title: 'Something went wrong',
+  }
+)
+
+const { isDark } = useTheme()
+
+const error = ref<Error | null>(null)
+
+const errorMessage = ref('')
+
+onErrorCaptured((err: Error) => {
+  error.value = err
+  errorMessage.value = err.message || 'An unexpected error occurred'
+  console.error('[ErrorBoundary]', err)
+  return false
+})
+
+function reset() {
+  error.value = null
+  errorMessage.value = ''
+}
+</script>