feat(content): comprehensive extraction hardening, code mode UI, overnight plan

- Relax isBookLikeResponse threshold (>=2 to >=1)
- Widen book patterns: inline prose, verb-preceded, numbered bold, em-dash
- Remove overly aggressive film/song gating on book extraction
- Allow songs to coexist with film/book tags (explicit tags always returned)
- Strengthen TV patterns: seasons, created by, standalone "tv" query match
- Fix TV_EXT_RE to handle both Title|Year|Creator and Title|Creator|Year
- Widen place patterns: type word search in descriptions, bold fallback
- Add "pizza" to isPlaceQuery and preferredFirstTab
- Add Code tab: isCodeQuery, isCodeLikeResponse, extractCodeBlocks, wiring
- Fix image threshold: single image with meaningful alt text shown
- Refactor filterTabsByContext: specialized paths now append remaining content
- Add code mode UI: orange input styling, design system selection, file selection
- DesignSystemGrid: selection toggle only on checkmark, card click opens detail
- Add 64-test extraction quality test suite
- Update overnight plan.md and prompt.md for hardening run

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

packages/app/src/components/content/DesignSystemGrid.vue

@@ -37,12 +37,29 @@
         <button
           v-for="item in filteredItems"
           :key="item.id"
-          class="text-left p-3 rounded-xl transition-colors group cursor-pointer"
-          :class="isDark
-            ? 'bg-white/[0.03] hover:bg-white/[0.07]'
-            : 'bg-black/[0.02] hover:bg-black/[0.05]'"
+          class="text-left p-3 rounded-xl transition-all duration-150 group relative"
+          :class="[
+            codeMode && isDesignTokenSelected(item.id)
+              ? 'ring-2 ring-accent/50 bg-accent/10 cursor-pointer'
+              : isDark
+                ? 'bg-white/[0.03] hover:bg-white/[0.07] cursor-pointer'
+                : 'bg-black/[0.02] hover:bg-black/[0.05] cursor-pointer',
+          ]"
           @click="selectItem(item)"
         >
+          <!-- Selection toggle (top-right) — only this area toggles context selection -->
+          <div
+            v-if="codeMode"
+            class="absolute top-2 right-2 w-5 h-5 rounded-full flex items-center justify-center z-10 cursor-pointer transition-colors"
+            :class="isDesignTokenSelected(item.id)
+              ? 'bg-accent'
+              : isDark ? 'bg-white/10 hover:bg-white/20' : 'bg-black/10 hover:bg-black/20'"
+            @click.stop="toggleDesignToken(item.id)"
+          >
+            <svg v-if="isDesignTokenSelected(item.id)" class="w-3 h-3 text-white" fill="none" stroke="currentColor" viewBox="0 0 24 24">
+              <path stroke-linecap="round" stroke-linejoin="round" stroke-width="3" d="M5 13l4 4L19 7" />
+            </svg>
+          </div>
           <!-- Preview swatch for colors -->
           <div v-if="item.category === 'colors' && item.preview === 'inline'"
                class="h-8 rounded-md mb-2 border"
@@ -92,9 +109,11 @@
 import { ref, computed } from 'vue'
 import { useTheme } from '@/composables/useTheme'
 import { useContentPanel, type DesignSystemItem } from '@/composables/useContentPanel'
+import { useCodeContext } from '@/composables/useCodeContext'
 
 const { isDark } = useTheme()
 const { openDesignSystemItem } = useContentPanel()
+const { codeMode, toggleDesignToken, isDesignTokenSelected } = useCodeContext()
 
 const activeCategory = ref<string>('all')