Add novel-writing app: .NET 10 API, React front end, agent and MCP server

Builds out the vertical slice for planning and writing a novel. Three front
ends — the React UI, an embedded Claude agent, and an MCP stdio server — all go
through one REST API, so an edit made from Claude Code and one made in the
browser are the same edit.

Layout:
  Domain          entities and enums, no dependencies
  Application     services, DTOs, the agent tool-use loop and its 15 tools
  Infrastructure  EF Core 10 + SQLite, Anthropic SDK client
  Api             ASP.NET Core 10 minimal APIs, OpenAPI, ProblemDetails
  Mcp             MCP stdio server, 21 tools over the same REST API
  Web             React 19 + Vite + TanStack Query + Tailwind v4

Data model is Project > Characters / OutlineNodes / Chapters > Scenes, plus
agent conversations. The outline is a self-nesting tree so acts, sequences and
beats can be arranged however the book wants; scenes carry goal/conflict/outcome
because that is what the agent drafts prose from.

Notes on a few choices:

- Conversation history replays to the model as text only. The agent re-reads
  current state through its tools rather than trusting a record of edits that
  may since have changed in the UI.
- The user's turn is persisted before the tool loop runs, so a question is
  recorded even when the model call fails. Turn order uses an explicit sequence
  column; timestamps tie when a turn completes inside one tick.
- Tool failures return is_error results rather than throwing, so the model can
  read the message and correct itself. MCP tools do the same via CallToolResult,
  which keeps the API's own message instead of a generic SDK error.
- The Anthropic client is constructed lazily. It is injected into the agent
  service, which also serves read-only endpoints, and those should keep working
  on an install with no key. Sending without one returns 503, not 400.
- DateTimeOffset is stored as UTC ticks. SQLite refuses to ORDER BY the default
  text form, which every "recently updated first" listing depends on.

Tests run against real in-memory SQLite rather than the EF in-memory provider so
they exercise the cascade deletes and query translation that actually ship.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01S56bfZMGe1hnhpWP4CjjNw

tests/NovelSoftware.Tests/NovelSoftware.Tests.csproj

@@ -0,0 +1,27 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="coverlet.collector" Version="6.0.4" />
+    <PackageReference Include="FluentAssertions" Version="7.2.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.1.4" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\NovelSoftware.Infrastructure\NovelSoftware.Infrastructure.csproj" />
+    <ProjectReference Include="..\..\src\NovelSoftware.Api\NovelSoftware.Api.csproj" />
+  </ItemGroup>
+
+</Project>