Eingehende Ausloeser: n8n und andere starten Agenten (#725, Stufe 1)

Something outside hands an agent a task - an n8n workflow on a mail, a
schedule, a form, or any system that sends an HTTP request.

- Core/Triggers/InboundTriggers: one token per trigger and agent, kept as a
  hash and shown once; a rate per hour; deliveries up to 64 KB. Each
  delivery becomes a task whose content is framed as foreign content with its
  origin; every delivery, accepted or refused, is in the audit (source
  "trigger").
- POST /hooks/trigger on the instance (MCP socket, own token, no browsers);
  the manager forwards /hooks/{instance}/trigger. /api/triggers to issue,
  list and revoke.
- Agent view: a triggers card with the address and an n8n/curl example.
- Nothing writes back: no right to create or change workflows.

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

src/ClawdDotNet.Web/Endpoints/McpEndpoints.cs

@@ -61,6 +61,60 @@ internal static class McpEndpoints
                 : Results.Text(answer, "application/json");
         });
 
+        // #725: An inbound trigger — n8n or any system that sends a request. Outside /api: its
+        // own token is the key, and it can do one thing — hand its agent a task.
+        app.MapPost(Security.McpTransport.TriggerPath, async (HttpContext context, AppHost host, CancellationToken ct) =>
+        {
+            if (context.Request.Headers.Origin.Count > 0)
+                return Results.StatusCode(StatusCodes.Status403Forbidden);
+            if (host.Triggers is not { } triggers)
+                return ApiEndpoints.Unavailable("No inbound triggers in this instance.");
+            if (context.Request.ContentLength is > Core.Triggers.InboundTriggers.MaxPayloadBytes)
+                return Results.StatusCode(StatusCodes.Status413PayloadTooLarge);
+
+            string payload;
+            using (var reader = new StreamReader(context.Request.Body))
+            {
+                var buffer = new char[Core.Triggers.InboundTriggers.MaxPayloadBytes + 1];
+                var read = await reader.ReadBlockAsync(buffer.AsMemory(), ct);
+                if (read > Core.Triggers.InboundTriggers.MaxPayloadBytes)
+                    return Results.StatusCode(StatusCodes.Status413PayloadTooLarge);
+                payload = new string(buffer, 0, read);
+            }
+
+            var result = await triggers.ReceiveAsync(BearerToken(context.Request), payload, ct);
+            return result.Outcome switch
+            {
+                Core.Triggers.TriggerOutcome.Accepted => Results.Json(new { ok = true, taskId = result.TaskId }, statusCode: StatusCodes.Status202Accepted),
+                Core.Triggers.TriggerOutcome.Unauthorized => Results.Json(new { ok = false, error = result.Message }, statusCode: StatusCodes.Status401Unauthorized),
+                Core.Triggers.TriggerOutcome.Limited => Results.Json(new { ok = false, error = result.Message }, statusCode: StatusCodes.Status429TooManyRequests),
+                Core.Triggers.TriggerOutcome.TooLarge => Results.StatusCode(StatusCodes.Status413PayloadTooLarge),
+                _ => Results.Json(new { ok = false, error = result.Message }, statusCode: StatusCodes.Status503ServiceUnavailable)
+            };
+        });
+
+        var triggerAdmin = app.MapGroup("/api/triggers");
+
+        triggerAdmin.MapGet("/", async (AppHost host, CancellationToken ct) =>
+            host.Triggers is { } triggers
+                ? Results.Ok((await triggers.ListAsync(ct)).Select(t => new TriggerDto(t.Id, t.Label, t.AgentId, t.PerHour, t.CreatedAtUtc, t.RevokedAtUtc, t.LastUsedAtUtc, t.Received, t.Active)).ToList())
+                : Results.Ok(Array.Empty<TriggerDto>()));
+
+        triggerAdmin.MapPost("/", async (AppHost host, TriggerInputDto input, CancellationToken ct) =>
+        {
+            if (host.Triggers is not { } triggers)
+                return ApiEndpoints.Unavailable("No inbound triggers in this instance.");
+            if (!host.Instance.Agents.Any(a => string.Equals(a.AgentId, input.AgentId, StringComparison.OrdinalIgnoreCase)))
+                return Results.BadRequest(new OutcomeDto(false, $"There is no agent '{input.AgentId}'."));
+            var (t, token) = await triggers.IssueAsync(input.Label ?? "", input.AgentId, input.PerHour ?? 30, ct);
+            return Results.Ok(new TriggerIssuedDto(new TriggerDto(t.Id, t.Label, t.AgentId, t.PerHour, t.CreatedAtUtc, null, null, 0, true), token));
+        });
+
+        triggerAdmin.MapDelete("/{id}", async (AppHost host, string id, CancellationToken ct) =>
+            host.Triggers is { } triggers && await triggers.RevokeAsync(id, ct)
+                ? Results.Ok(new OutcomeDto(true, "Revoked."))
+                : Results.NotFound(new OutcomeDto(false, $"No active trigger '{id}'.")));
+
         // Streamable HTTP lets a server refuse the event stream; this one keeps no sessions.
         app.MapMethods("/mcp", ["GET", "DELETE"], () => Results.StatusCode(StatusCodes.Status405MethodNotAllowed));