Implement CBOR Extended Diagnostic Notation (EDN) export functionality

[Copilot]

This PR adds support for exporting CBOR data to Extended Diagnostic Notation (EDN) format, a human-readable text representation of CBOR data as specified in the CBOR RFC.

What's Added

The implementation introduces a new CborEdn class in src/cbor/CborEdn.ts that provides methods to convert JavaScript values and CBOR-encoded data to EDN string format.

Core API

import { CborEdn, CborEncoder, CborDecoder } from '@jsonjoy.com/json-pack/lib/cbor';

const edn = new CborEdn();

// Format JavaScript values as EDN
console.log(edn.encode(42)); // "42"
console.log(edn.encode("hello")); // '"hello"'
console.log(edn.encode([1, 2, 3])); // "[1, 2, 3]"
console.log(edn.encode({a: 1, b: 2})); // '{"a": 1, "b": 2}'

// Format byte strings
console.log(edn.encode(new Uint8Array([0x01, 0x02, 0x03]))); // "h'010203'"

// Format CBOR-encoded data directly
const encoder = new CborEncoder();
const decoder = new CborDecoder();
const cborBytes = encoder.encode({name: "Alice", age: 30});
console.log(edn.formatCbor(cborBytes, decoder)); // '{"name": "Alice", "age": 30}'

Supported Data Types

The implementation handles all CBOR data types with proper EDN representation:

• Numbers: integers, floats, BigInt, special values (NaN, ±Infinity, -0.0)
• Strings: JSON-style escaping, Unicode support, carriage return removal per spec
• Byte strings: hex notation (h'...') representation
• Arrays: standard JSON-like syntax with proper nesting
• Objects: standard JSON object notation
• Maps: supports any key type as per CBOR specification
• Tags: CBOR tag notation (tag(content))
• Simple values: true/false, null/undefined, custom simple values

Examples

// Complex nested structures
const complex = {
  metadata: {
    timestamp: new JsonPackExtension(1, 1609459200), // CBOR timestamp tag
    flags: new Uint8Array([0x01, 0x02, 0x03])
  },
  users: [{id: 1, name: 'Alice'}, {id: 2, name: 'Bob'}],
  settings: new Map([['debug', true], [42, 'answer']])
};

console.log(edn.encode(complex));
// Output: {"metadata": {"timestamp": 1(1609459200), "flags": h'010203'}, "users": [{"id": 1, "name": "Alice"}, {"id": 2, "name": "Bob"}], "settings": {"debug": true, 42: "answer"}}

Testing

The implementation includes comprehensive test coverage:

• 37 test cases covering all EDN features and edge cases
• Integration tests with CBOR encoder/decoder roundtrip verification
• Manual verification with complex nested data structures
• All existing CBOR tests (767) continue to pass

Documentation

Updated the CBOR module README with EDN usage examples and API documentation.

This is an additive feature that doesn't modify any existing CBOR encoding/decoding logic, ensuring full backward compatibility.

Fixes #30.

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