feat: detect host operating system at startup and provide platform-specific guidance

MeetingAssistant/Workflow/WorkflowRulesEditorInstructionBuilder.cs

@@ -38,10 +38,14 @@ public sealed class WorkflowRulesEditorInstructionBuilder : IWorkflowRulesEditor
         Explain the final change briefly after the tools finish.
         """;
 
+    private readonly HostOperatingSystem hostOperatingSystem;
     private readonly ILogger<WorkflowRulesEditorInstructionBuilder> logger;
 
-    public WorkflowRulesEditorInstructionBuilder(ILogger<WorkflowRulesEditorInstructionBuilder> logger)
+    public WorkflowRulesEditorInstructionBuilder(
+        HostOperatingSystem hostOperatingSystem,
+        ILogger<WorkflowRulesEditorInstructionBuilder> logger)
     {
+        this.hostOperatingSystem = hostOperatingSystem;
         this.logger = logger;
     }
 
@@ -53,8 +57,10 @@ public sealed class WorkflowRulesEditorInstructionBuilder : IWorkflowRulesEditor
             : editorOptions.InitialPrompt!;
         var rulesPath = WorkflowRulesPathResolver.Resolve(options.Automation.RulesPath) ?? "<not configured>";
         var docs = await ReadWorkflowDocsAsync(cancellationToken);
+        var platformGuidance = BuildPlatformGuidance(hostOperatingSystem);
 
         return configuredPrompt.Trim() + Environment.NewLine + Environment.NewLine +
+            platformGuidance + Environment.NewLine + Environment.NewLine +
             $"Configured workflow rules file: {rulesPath}" + Environment.NewLine + Environment.NewLine +
             "Configuration tools can read and replace the local appsettings JSON file. Use read_config_docs for the configuration reference." + Environment.NewLine + Environment.NewLine +
             "Log tools can read and search the current application-owned log file and four rotated older files under the temp log folder." + Environment.NewLine + Environment.NewLine +
@@ -69,6 +75,28 @@ public sealed class WorkflowRulesEditorInstructionBuilder : IWorkflowRulesEditor
             "```";
     }
 
+    private static string BuildPlatformGuidance(HostOperatingSystem operatingSystem)
+    {
+        var platformGuidance = operatingSystem.Kind switch
+        {
+            HostOperatingSystemKind.Windows => """
+                Detected host operating system: Windows.
+                Use Windows-native operational guidance: PowerShell and native Windows commands, Windows-style paths, Windows environment-variable conventions, Windows services and processes, and Task Manager. Do not use macOS-only commands or concepts.
+                """,
+            HostOperatingSystemKind.MacOS => """
+                Detected host operating system: macOS.
+                Use macOS-native operational guidance: zsh and native macOS commands, POSIX-style paths, macOS environment-variable conventions, launchd and LaunchAgents, application processes, and Activity Monitor. Do not use Windows-only commands or concepts.
+                """,
+            _ => """
+                Detected host operating system: unsupported.
+                Use portable .NET concepts. Do not assume Windows or macOS commands, paths, services, environment conventions, or desktop features.
+                """
+        };
+
+        return platformGuidance + Environment.NewLine +
+            "Prefer the provided Meeting Assistant tools over shell commands when a matching tool exists. Operating-system detection selects appropriate guidance; it does not make unavailable integrations available.";
+    }
+
     private async Task<string> ReadWorkflowDocsAsync(CancellationToken cancellationToken)
     {
         foreach (var path in RuntimeContentLocator.CandidateDocumentationPaths("meeting-workflow-engine.md"))