Optimize SchemaId serialization and improve code formatting

Agent-Logs-Url: https://github.com/fsprojects/FSharp.Data.GraphQL/sessions/fec46b15-afce-40da-85b4-306eae430ce0

Co-authored-by: xperiandri <2365592+xperiandri@users.noreply.github.com>

Author: Copilot

src/FSharp.Data.GraphQL.Shared/ValidationResultCache.fs

@@ -3,9 +3,12 @@ namespace FSharp.Data.GraphQL.Validation
 open FSharp.Data.GraphQL
 open FSharp.Data.GraphQL.Types.Introspection
 open System
+open System.IO
 open System.Security.Cryptography
 open System.Text
+open System.Text.Encodings.Web
 open System.Text.Json
+open System.Text.Json.Serialization
 
 type ValidationResultKey =
     { DocumentId : string
@@ -18,16 +21,17 @@ type IValidationResultCache =
     abstract GetOrAdd : ValidationResultProducer -> ValidationResultKey -> ValidationResult<GQLProblemDetails>
 
 module SchemaId =
+
     let private formatByteAsLowerHex (value : byte) =
         value.ToString("x2", System.Globalization.CultureInfo.InvariantCulture)
 
     // Note: UnsafeRelaxedJsonEscaping is used here only for deterministic hashing,
     // not for output to untrusted contexts. The JSON is never exposed externally.
     let private jsonOptions = JsonSerializerOptions(
         WriteIndented = false,
-        DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.Never,
+        DefaultIgnoreCondition = JsonIgnoreCondition.Never,
         PropertyNamingPolicy = null,
-        Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping
+        Encoder = JavaScriptEncoder.UnsafeRelaxedJsonEscaping
     )
 
     /// <summary>
@@ -36,12 +40,13 @@ module SchemaId =
     /// <param name="introspectionSchema">The introspection schema to hash.</param>
     /// <returns>A lowercase hexadecimal SHA-256 hash string that uniquely identifies the schema structure.</returns>
     let fromIntrospectionSchema (introspectionSchema : IntrospectionSchema) =
-        let json = JsonSerializer.Serialize(introspectionSchema, jsonOptions)
-        let jsonBytes = Encoding.UTF8.GetBytes json
+        use stream = new MemoryStream()
+        JsonSerializer.Serialize(stream, introspectionSchema, jsonOptions)
+        stream.Position <- 0L
         // Note: Creating SHA256 instance per call is acceptable since schema ID computation
         // happens infrequently (typically once per schema during validation cache key creation)
         use sha256 = SHA256.Create()
-        let hash = sha256.ComputeHash jsonBytes
+        let hash = sha256.ComputeHash stream
         hash
         |> Seq.map formatByteAsLowerHex
         |> String.concat ""