Remove Scenes, group beats by multiple characters; strip comments repo-wide

Drop the Scene entity/grouping in favor of chapters carrying prose directly
and beats belonging to many characters. Add markdown editor + character
multi-select components to the web client. Remove all XML doc and inline
comments across the touched C#/TS/CSS files in favor of self-documenting
names, and record that convention in CLAUDE.md. Add .mcp.json (local MCP
server config, no secrets) and ignore .idea/.

tests/Novelly.Api.Tests/ExceptionHandlingTests.cs

@@ -5,11 +5,6 @@ using Novelly.Api.Projects;
 
 namespace Novelly.Api.Tests;
 
-/// <summary>
-/// Covers the exception-handling rework: a missing entity is an ordinary result, not a
-/// thrown exception; <see cref="Guard"/> rejects missing required arguments; and a
-/// service re-validates a request even when a direct caller skips the API's own filter.
-/// </summary>
 [TestFixture]
 public class ExceptionHandlingTests : ServiceTestFixture
 {