docs: add growth page features to CLAUDE.md

Document the growth page components, state management, color codes, and layout order.

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

CLAUDE.md

@@ -65,10 +65,36 @@ docs/                     # Design docs
 - **Sessions:** Login sessions with httpOnly cookies
 - **Logs:** Feed, sleep, diaper entries with timestamps
 - **Vaccinations:** IAP schedule tracking
-- **Growth:** Weight/height over time
+- **Growth:** Weight/height/head measurements over time
 - **Memories:** Photos with R2 storage
 - **Chat Sessions:** User conversations with AI (chat_sessions, chat_messages)
 
+### Growth Page Features
+
+The growth page tracks child's physical development with WHO standards.
+
+**Components:**
+- `formatAge(birthDate, measurementDate?)` - Shows age as "1y 4mo" or "8mo"
+- Latest Reading card with velocity and percentile
+- WHO Standards collapsible card (shows icons ⚖️📏⭕ when collapsed)
+- Growth chart (collapsible inside WHO card)
+- History (collapsible with scroll for many entries)
+- Goals stored in localStorage (`tia_growth_goal_${childId}`)
+
+**State:**
+- `showAdd` - Toggle add form (only shows if latest exists)
+- `showGoals` - Toggle goals card
+- `showWhoStandards` - Toggle WHO card expand/collapse
+- `showChart` - Toggle chart inside WHO card
+- `showHistory` - Toggle history expand/collapse
+
+**Color-coded percentiles:**
+- 🟢 Normal (15th-85th percentile)
+- 🟡 Watch (<15th or >85th)
+- 🔴 Alert (<3rd or >97th)
+
+**Column order:** Goals → Latest → Add Form → WHO+Chart → History
+
 ### Key Patterns
 
 **ThemeProvider:** Wrap app in ThemeProvider from layout.tsx. Use `useTheme()` hook in components.