Add Policy DSL Validator, Schema Exporter, and Simulation Smoke tools

- Implemented PolicyDslValidator with command-line options for strict mode and JSON output.
- Created PolicySchemaExporter to generate JSON schemas for policy-related models.
- Developed PolicySimulationSmoke tool to validate policy simulations against expected outcomes.
- Added project files and necessary dependencies for each tool.
- Ensured proper error handling and usage instructions across tools.

tools/PolicySchemaExporter/PolicySchemaExporter.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="NJsonSchema" Version="11.5.1" />
+    <PackageReference Include="NJsonSchema.SystemTextJson" Version="11.5.1" />
+    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\StellaOps.Scheduler.Models\StellaOps.Scheduler.Models.csproj" />
+  </ItemGroup>
+
+</Project>

tools/PolicySchemaExporter/Program.cs

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+using System.Collections.Immutable;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+using NJsonSchema;
+using NJsonSchema.Generation;
+using NJsonSchema.Generation.SystemTextJson;
+using Newtonsoft.Json;
+using StellaOps.Scheduler.Models;
+
+var output = args.Length switch
+{
+    0 => Path.GetFullPath(Path.Combine(AppContext.BaseDirectory, "..", "..", "..", "docs", "schemas")),
+    1 => Path.GetFullPath(args[0]),
+    _ => throw new ArgumentException("Usage: dotnet run --project tools/PolicySchemaExporter -- [outputDirectory]")
+};
+
+Directory.CreateDirectory(output);
+
+var generatorSettings = new SystemTextJsonSchemaGeneratorSettings
+{
+    SchemaType = SchemaType.JsonSchema,
+    DefaultReferenceTypeNullHandling = ReferenceTypeNullHandling.NotNull,
+    SerializerOptions = new JsonSerializerOptions
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+    },
+};
+
+var generator = new JsonSchemaGenerator(generatorSettings);
+
+var exports = ImmutableArray.Create(
+    (FileName: "policy-run-request.schema.json", Type: typeof(PolicyRunRequest)),
+    (FileName: "policy-run-status.schema.json", Type: typeof(PolicyRunStatus)),
+    (FileName: "policy-diff-summary.schema.json", Type: typeof(PolicyDiffSummary)),
+    (FileName: "policy-explain-trace.schema.json", Type: typeof(PolicyExplainTrace))
+);
+
+foreach (var export in exports)
+{
+    var schema = generator.Generate(export.Type);
+    schema.Title = export.Type.Name;
+    schema.AllowAdditionalProperties = false;
+
+    var outputPath = Path.Combine(output, export.FileName);
+    await File.WriteAllTextAsync(outputPath, schema.ToJson(Formatting.Indented) + Environment.NewLine);
+    Console.WriteLine($"Wrote {outputPath}");
+}