Fix JSON encoding: Disable forward slash escaping

MCP servers cannot handle escaped forward slashes (\/) in paths.
Changed JSONEncoder to use .withoutEscapingSlashes formatting.

This fixes tool execution timeouts where tools/call requests were
sent but servers never responded due to malformed path arguments.

Bug: Path '/Users/...' was encoded as '\/Users\/...' causing 30s timeout

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

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

Author: dcherrera

Sources/MCP/Client/Client.swift

@@ -155,7 +155,11 @@ public actor Client {
     /// A dictionary of type-erased pending requests, keyed by request ID
     private var pendingRequests: [ID: AnyPendingRequest] = [:]
     // Add reusable JSON encoder/decoder
-    private let encoder = JSONEncoder()
+    private let encoder: JSONEncoder = {
+        let encoder = JSONEncoder()
+        encoder.outputFormatting = .withoutEscapingSlashes
+        return encoder
+    }()
     private let decoder = JSONDecoder()
 
     public init(