Add outline import feature; drop Dto naming, map entities at the API boundary

Services now return entities; endpoints (and the agent toolsets) map to
*Response records instead of services building wire DTOs themselves.
Also brings in the outline-import agent, MCP tool, ledger and web dialog
that were already in progress on disk.

tests/Novelly.Api.Tests/NovelAgentServiceTests.cs

@@ -31,7 +31,7 @@ public class NovelAgentServiceTests : ServiceTestFixture
 
         var turn = await agent.SendMessageAsync(projectId, new SendAgentMessageRequest("Where do I start?"));
 
-        Assert.That(turn.Message.Content, Is.EqualTo("Tell me about the ending."));
+        Assert.That(turn.Content, Is.EqualTo("Tell me about the ending."));
 
         var conversation = (await agent.GetConversationAsync(turn.ConversationId))!;
 
@@ -62,9 +62,9 @@ public class NovelAgentServiceTests : ServiceTestFixture
         {
             Assert.That(characters, Has.Count.EqualTo(1));
             Assert.That(characters[0].Name, Is.EqualTo("Ines"));
-            Assert.That(turn.Message.Content, Is.EqualTo("Added Ines as the protagonist."));
-            Assert.That(turn.Message.ToolCalls, Has.Count.EqualTo(1));
-            Assert.That(turn.Message.ToolCalls[0].Name, Is.EqualTo("create_character"));
+            Assert.That(turn.Content, Is.EqualTo("Added Ines as the protagonist."));
+            Assert.That(turn.ToResponse().ToolCalls, Has.Count.EqualTo(1));
+            Assert.That(turn.ToResponse().ToolCalls[0].Name, Is.EqualTo("create_character"));
         });
     }
 
@@ -113,7 +113,7 @@ public class NovelAgentServiceTests : ServiceTestFixture
         {
             Assert.That(errorResult.IsError, Is.True);
             Assert.That(errorResult.Content, Does.Contain("was not found"));
-            Assert.That(turn.Message.Content, Does.Contain("does not exist yet"));
+            Assert.That(turn.Content, Does.Contain("does not exist yet"));
         });
     }
 
@@ -154,7 +154,7 @@ public class NovelAgentServiceTests : ServiceTestFixture
         Assert.Multiple(() =>
         {
             Assert.That(model.Transcripts, Has.Count.EqualTo(4));
-            Assert.That(turn.Message.Content, Does.Contain("tool-call limit"));
+            Assert.That(turn.Content, Does.Contain("tool-call limit"));
         });
     }