Upgrade Serde to 1.0.0 (#7)

## Upgrade Serde to 0.9.1

Upgrades Serde from `[0.8.0,0.9.0)` to `0.9.1`.

## API Changes

**Signature Updates:**
- `TryReadIndex(ISerdeInfo, out string?)` split into two methods:
  - `TryReadIndex(ISerdeInfo)` - returns just the index
  - `TryReadIndexWithName(ISerdeInfo)` - returns tuple `(int, string?)`

All other APIs remain the same as 0.8.x.

## Status
✅ Main library builds successfully
✅ All tests pass
✅ Benchmarks build successfully

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<details>

<summary>Original prompt</summary>

> Please upgrade to the latest serde version


</details>



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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: agocke <515774+agocke@users.noreply.github.com>
Co-authored-by: Andy Gocke <andy@commentout.net>

Author: Copilot

Directory.Packages.props

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="BenchmarkDotNet" Version="0.14.0" />
-    <PackageVersion Include="Serde" Version="[0.8.0,0.9.0)" />
+    <PackageVersion Include="Serde" Version="0.9.1" />
     <PackageVersion Include="Spectre.Console" Version="0.54.0" />
     <PackageVersion Include="StaticCs" Version="0.3.1" />
     <PackageVersion Include="Spectre.Console.Testing" Version="0.54.0" />

src/Deserializer.cs

@@ -14,12 +14,17 @@ internal sealed partial class Deserializer(string[] args, bool handleHelp) : IDe
 
     public IReadOnlyList<ISerdeInfo> HelpInfos => _helpInfos;
 
-    int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
+    int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo)
+    {
+        var (index, _) = ((ITypeDeserializer)this).TryReadIndexWithName(serdeInfo);
+        return index;
+    }
+
+    (int, string? errorName) ITypeDeserializer.TryReadIndexWithName(ISerdeInfo serdeInfo)
     {
         if (_argIndex == args.Length)
         {
-            errorName = null;
-            return ITypeDeserializer.EndOfType;
+            return (ITypeDeserializer.EndOfType, null);
         }
 
         var arg = args[_argIndex];
@@ -29,8 +34,7 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
             _helpInfos.Add(serdeInfo);
             if (_argIndex == args.Length)
             {
-                errorName = null;
-                return ITypeDeserializer.EndOfType;
+                return (ITypeDeserializer.EndOfType, null);
             }
             arg = args[_argIndex];
         }
@@ -50,8 +54,7 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
                         if (arg == flag)
                         {
                             _argIndex++;
-                            errorName = null;
-                            return fieldIndex;
+                            return (fieldIndex, null);
                         }
                     }
                 }
@@ -61,8 +64,7 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
                          commandName == arg)
                 {
                     _argIndex++;
-                    errorName = null;
-                    return fieldIndex;
+                    return (fieldIndex, null);
                 }
                 else if (!arg.StartsWith('-') &&
                          attr is { AttributeType: { Name: nameof(CommandGroupAttribute) } })
@@ -84,15 +86,14 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
                     _throwOnMissing = false;
 
                     var deType = this.ReadType(fieldInfo);
-                    int index = deType.TryReadIndex(fieldInfo, out _);
+                    int index = deType.TryReadIndex(fieldInfo);
                     _argIndex = savedIndex;
                     _throwOnMissing = savedThrowOnMissing;
 
                     if (index >= 0)
                     {
                         // We found a match, so we can return the field index.
-                        errorName = null;
-                        return fieldIndex;
+                        return (fieldIndex, null);
                     }
                     // No match, so we can continue.
                 }
@@ -102,8 +103,7 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
                          _paramIndex == paramIndex)
                 {
                     _paramIndex++;
-                    errorName = null;
-                    return fieldIndex;
+                    return (fieldIndex, null);
                 }
             }
         }
@@ -113,8 +113,7 @@ int ITypeDeserializer.TryReadIndex(ISerdeInfo serdeInfo, out string? errorName)
         }
         else
         {
-            errorName = arg;
-            return ITypeDeserializer.IndexNotFound;
+            return (ITypeDeserializer.IndexNotFound, arg);
         }
     }