feat: add use cases marketing product with AI-generated content

Transform qualifying scenarios into marketing-ready use cases with:
- AI-generated titles, descriptions, ROI estimates, business value
- Persona/industry/category taxonomy for targeting
- Browseable feed with filtering and ranking
- SEO-optimized case study pages
- Daily cron job for generation and ranking

Database:
- Add Persona, Industry, Category lookup tables
- Add UseCase model with marketing content fields
- Add junction tables for personas/industries/categories
- Add SocialProof model for cached metrics

API:
- GET /api/use-cases - Global directory with filtering
- GET /api/use-cases/[id] - Individual use case details
- GET /api/public/users/[username]/collections/[slug]/use-cases
- POST /api/cron/use-cases - Nightly generation job

Frontend:
- /use-cases - Global feed with persona dropdown
- /use-cases/[slug] - SEO case study page
- /[username]/collections/[slug]/use-cases - Collection feed
- UseCasesFeed component - Sortable table component
- UseCaseCaseStudy component - Full case study layout

packages/tools/official/text-chunk/src/index.ts

@@ -76,14 +76,14 @@ function chunkBySentences(
       if (overlap > 0) {
         // Calculate how many sentences to include for overlap
         let overlapText = '';
-        let overlapSentences = 0;
+        let _overlapSentences = 0;
 
         for (let j = i - 1; j >= 0 && overlapText.length < overlap; j--) {
           const overlapSentence = sentences[j];
           if (!overlapSentence) continue;
           if (overlapText.length + overlapSentence.length <= overlap) {
             overlapText = `${overlapSentence} ${overlapText}`;
-            overlapSentences++;
+            _overlapSentences++;
           } else {
             break;
           }
@@ -221,7 +221,7 @@ export const textChunkTool = tool({
       if (chunks.length === 0) {
         chunks = chunkBySize(text, maxChunkSize, overlap);
       }
-    } catch (error) {
+    } catch (_error) {
       // Fall back to simple size-based chunking if sentence detection fails
       chunks = chunkBySize(text, maxChunkSize, overlap);
     }