feat: JSON/JSONB validation, multi-column indexes, CTE execution, wire protocol column types

- Add fkJson to wire protocol with serialization/deserialization
- Validate JSON/JSONB on INSERT/UPDATE via std/json
- Send real column type metadata in wire protocol responses
- Update all 4 clients (Nim, Python, JS, Rust) for JSON and columnTypes
- Implement multi-column index parser (CREATE INDEX idx ON t(a, b))
- Add ciColumns to AST nkCreateIndex
- Build composite index keys as table.col1.col2 with val1|val2
- Support multi-column exact match in SELECT for AND chains
- Implement non-recursive CTE execution via ctx.cteTables materialization
- Add tkRecursive token and parse WITH RECURSIVE
- Fix test isolation: use temp dirs for JOIN, migration, and RLS tests
- All tests passing (0 failures)

clients/javascript/baradb.js

@@ -46,6 +46,7 @@ const FieldKind = {
   ARRAY: 0x0A,
   OBJECT: 0x0B,
   VECTOR: 0x0C,
+  JSON: 0x0D,
 };
 
 const ResultFormat = {
@@ -57,6 +58,7 @@ const ResultFormat = {
 class QueryResult {
   constructor() {
     this.columns = [];
+    this.columnTypes = [];
     this.rows = [];
     this.rowCount = 0;
     this.affectedRows = 0;
@@ -169,6 +171,12 @@ class Client {
         pos += sLen;
       }
       result.columns = cols;
+      const colTypes = [];
+      for (let i = 0; i < colCount; i++) {
+        colTypes.push(payload[pos]);
+        pos++;
+      }
+      result.columnTypes = colTypes;
       const rowCount = new DataView(payload.buffer).getUint32(pos, false);
       pos += 4;
       for (let r = 0; r < rowCount; r++) {
@@ -252,6 +260,13 @@ class Client {
         }
         break;
       }
+      case FieldKind.JSON: {
+        const len = new DataView(payload.buffer).getUint32(pos, false);
+        pos += 4;
+        result = new TextDecoder().decode(payload.slice(pos, pos + len));
+        pos += len;
+        break;
+      }
       default: result = null;
     }
     this._lastReadPos = pos;