Automatisierungsvorschlaege nur mit n8n-Anbindung (#726)

An instance without n8n has no use for workflow proposals. New instance
setting automation.enabled ("this instance works with n8n"), off by default:
- off: automation_find/automation_propose refuse, no candidates are put to
  agents, and the escalation tool does not mention proposals at all;
- the switch sits in the settings card for external MCP servers; the
  approvals view says proposals are off instead of standing empty.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/ClawdDotNet.Core/Automation/AutomationProposals.cs

@@ -9,6 +9,16 @@ using Microsoft.Extensions.Logging;
 
 namespace ClawdDotNet.Core.Automation;
 
+/// <summary>
+/// #726: Whether the instance works with n8n. Off by default: an instance without n8n has no
+/// use for workflow proposals, and every proposal and candidate costs runs and attention.
+/// </summary>
+public sealed class AutomationSettings
+{
+    [System.Text.Json.Serialization.JsonPropertyName("enabled")]
+    public bool Enabled { get; set; }
+}
+
 /// <summary>What the replaced tasks cost over the measured days — taken from the receipts, not estimated.</summary>
 public sealed record MeasuredSavings(int Days, int Runs, decimal CostUsd, long Tokens)
 {
@@ -32,6 +42,9 @@ public sealed record AutomationOutcome(bool Ok, string Message, long? Id = null)
 
 public interface IAutomationProposals
 {
+    /// <summary>Whether the instance works with n8n — without it, nothing is proposed.</summary>
+    bool Enabled { get; }
+
     Task<IReadOnlyList<AutomationProposal>> FindAsync(string subject, CancellationToken ct);
 
     Task<AutomationOutcome> ProposeAsync(AutomationRequest request, CancellationToken ct);
@@ -57,8 +70,13 @@ public sealed class AutomationProposals(
     ITaskRepository tasks,
     TaskboardService? board,
     ILogger logger,
+    Func<AutomationSettings>? settings = null,
     TimeProvider? clock = null) : IAutomationProposals, IAsyncDisposable
 {
+    public bool Enabled => settings?.Invoke().Enabled ?? true;
+
+    public const string DisabledMessage = "This instance does not work with n8n — workflow proposals are switched off.";
+
     public const int MaxOpenPerAgent = 3;
     public const int MeasureDays = 28;
 
@@ -85,6 +103,8 @@ public sealed class AutomationProposals(
 
     public async Task<AutomationOutcome> ProposeAsync(AutomationRequest r, CancellationToken ct)
     {
+        if (!Enabled)
+            return new(false, DisabledMessage);
         if (string.IsNullOrWhiteSpace(r.Purpose) || string.IsNullOrWhiteSpace(r.Trigger))
             return new(false, "'purpose' and 'trigger' are required — what it is for, and what starts it.");
         if (r.TaskIds.Count == 0)
@@ -236,7 +256,7 @@ public sealed class AutomationProposals(
     /// </summary>
     public async Task<IReadOnlyList<string>> FindCandidatesAsync(CancellationToken ct)
     {
-        if (board is null)
+        if (board is null || !Enabled)
             return [];
         var since = Now.AddDays(-CandidateDays);
         var proposals = await ListAsync(null, 1000, ct);

src/ClawdDotNet.Core/Config/InstanceConfig.cs

@@ -159,6 +159,10 @@ public sealed class InstanceConfig
     [JsonPropertyName("fileHistory")]
     public Files.FileHistorySettings FileHistory { get; set; } = new();
 
+    /// <summary>#726: Whether this instance works with n8n — only then do agents propose workflows. Off by default.</summary>
+    [JsonPropertyName("automation")]
+    public Automation.AutomationSettings Automation { get; set; } = new();
+
     /// <summary>#197: External MCP servers whose tools the agents may use — set up by a human only.</summary>
     [JsonPropertyName("mcpServers")]
     public List<Mcp.McpServerConfig> McpServers { get; set; } = new();