chore: vendor react-best-practices agent skill for cursor agents

Adds the Vercel skill under .agents with famapp path patterns.

Includes skills-lock.json pin.

.agents/skills/react-best-practices/rules/_template.md

@@ -0,0 +1,28 @@
+---
+title: Rule Title Here
+impact: MEDIUM
+impactDescription: Optional description of impact (e.g., "20-50% improvement")
+tags: tag1, tag2
+---
+
+## Rule Title Here
+
+**Impact: MEDIUM (optional impact description)**
+
+Brief explanation of the rule and why it matters. This should be clear and concise, explaining the performance implications.
+
+**Incorrect (description of what's wrong):**
+
+```typescript
+// Bad code example here
+const bad = example();
+```
+
+**Correct (description of what's right):**
+
+```typescript
+// Good code example here
+const good = example();
+```
+
+Reference: [Link to documentation or resource](https://example.com)