docs: Add VERIFIED_FEATURES.md - tracking production-tested features

Documento que distingue features probadas en producción vs tests.
- Database operations (open, close, prepare, exec)
- Statement operations (step, columnInt, columnText)
- Extensiones (FTS5, JSON, R-Tree) marcadas como sin probar

Verificado en zsimifactu: SELECT con 510 registros, CREATE TABLE

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

VERIFIED_FEATURES.md

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+# VERIFIED_FEATURES.md - zcatsql
+
+Estado de verificación de funcionalidades en aplicaciones reales.
+
+**Leyenda:**
+- ✅ **Verificado** - Probado en aplicación real, funciona correctamente
+- ⚠️ **Tests only** - Solo tests unitarios, no probado en app real
+- 🔧 **Mejorado** - Probado y mejorado/corregido durante uso real
+- ❌ **Incompleto** - Conocido como incompleto o con limitaciones
+- ❓ **Sin probar** - No tiene tests ni uso real
+
+---
+
+## Core (database.zig / statement.zig)
+
+### Conexión y Base de Datos
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Database.open | ✅ | zsimifactu |
+| Database.close | ✅ | zsimifactu |
+| Database.prepare | ✅ | zsimifactu |
+| Database.exec | ✅ | zsimifactu - CREATE TABLE |
+| Database.lastInsertRowId | ⚠️ | Tests only |
+| Database.changes | ⚠️ | Tests only |
+
+### Statements
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Statement.prepare | ✅ | zsimifactu |
+| Statement.step | ✅ | zsimifactu - SELECT iteration |
+| Statement.reset | ⚠️ | Tests only |
+| Statement.finalize | ✅ | zsimifactu |
+| Statement.columnInt | ✅ | zsimifactu |
+| Statement.columnText | ✅ | zsimifactu |
+| Statement.columnFloat | ⚠️ | Tests only |
+| Statement.columnBlob | ⚠️ | Tests only |
+| Statement.bindInt | ⚠️ | Tests only |
+| Statement.bindText | ⚠️ | Tests only |
+| Statement.bindFloat | ⚠️ | Tests only |
+| Statement.bindNull | ⚠️ | Tests only |
+
+### Tipos de Datos
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| INTEGER | ✅ | zsimifactu |
+| TEXT | ✅ | zsimifactu |
+| REAL | ⚠️ | Tests only |
+| BLOB | ⚠️ | Tests only |
+| NULL handling | ✅ | zsimifactu - COALESCE |
+
+---
+
+## Extensiones
+
+### fts5.zig (Full-Text Search)
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| createFts5Table | ⚠️ | Tests only |
+| fts5Query | ⚠️ | Tests only |
+| fts5Highlight | ⚠️ | Tests only |
+
+### json.zig
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| JSON functions | ⚠️ | Tests only |
+| json_extract | ⚠️ | Tests only |
+| json_array | ⚠️ | Tests only |
+
+### rtree.zig (Spatial Index)
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Todas | ❓ | Sin probar |
+
+### vtable.zig (Virtual Tables)
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Todas | ❓ | Sin probar |
+
+---
+
+## Utilidades
+
+### backup.zig
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| backup | ⚠️ | Tests only |
+| restore | ⚠️ | Tests only |
+
+### pool.zig (Connection Pool)
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Pool.init | ⚠️ | Tests only |
+| Pool.acquire | ⚠️ | Tests only |
+| Pool.release | ⚠️ | Tests only |
+
+### functions.zig (Custom Functions)
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| createScalarFunction | ⚠️ | Tests only |
+| createAggregateFunction | ⚠️ | Tests only |
+
+### session.zig
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Todas | ❓ | Sin probar |
+
+### serialize.zig
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Todas | ❓ | Sin probar |
+
+### audit/
+| Feature | Estado | Notas |
+|---------|--------|-------|
+| Todas | ❓ | Sin probar |
+
+---
+
+## Historial de Verificación
+
+| Fecha | Proyecto | Features Verificadas |
+|-------|----------|---------------------|
+| 2025-12-09 | zsimifactu | open, close, prepare, exec, step, columnInt, columnText |
+| 2025-12-09 | zsimifactu | SELECT con 510 registros, CREATE TABLE, INSERT |
+
+---
+
+## Próximos a Verificar (Prioridad zsimifactu)
+
+1. **Bind parameters** - Para INSERT/UPDATE seguros
+2. **Transactions** - BEGIN/COMMIT/ROLLBACK
+3. **lastInsertRowId** - Para nuevos registros
+4. **FTS5** - Búsqueda de texto en clientes