feat: shelldocs init - scaffold ShellDocs into a Blazor project

[Shewart]

Summary

Implements the first real CLI command: shelldocs init. Detects a Blazor project in the target directory, adds ShellDocs.Components + ShellDocs.Tokens package references, drops in content/docs/ starter markdown + a routed DocsPage.razor, and writes a SHELLDOCS_SETUP.md with copy-paste snippets for Program.cs and App.razor. Idempotent — every write is skip-if-present.

What's in it

src/ShellDocs.Templates/ScaffoldTemplates.cs — raw-string constants for everything the CLI emits: introduction.md, meta.json, DocsPage.razor, and a parameterised SHELLDOCS_SETUP.md (takes siteName + githubRepo). Zero I/O beyond the string constants — the templates ARE the payload.

src/ShellDocs.CLI/Commands/InitCommand.cs — the orchestrator:

• Locates the .csproj in --dir (default cwd), errors cleanly if missing.
• Verifies it's a Blazor project (checks for Microsoft.NET.Sdk.Web / Microsoft.NET.Sdk.Razor / Microsoft.NET.Sdk.BlazorWebAssembly SDK, or an AspNetCore.Components package reference). Errors if not.
• Adds ShellDocs.Components + ShellDocs.Tokens package refs — inserts into an existing <ItemGroup> that already holds PackageReferences if possible, else appends a new <ItemGroup> before </Project>. Regex-guarded so it never duplicates.
• Ensures content/docs/ exists, writes introduction.md + meta.json if missing.
• Locates a Pages dir — prefers Components/Pages (modern Blazor Web App), falls back to Pages (classic Server / WASM). Creates Components/Pages if neither exists. Writes DocsPage.razor if missing.
• Writes SHELLDOCS_SETUP.md at the project root with the exact Program.cs and App.razor snippets to paste. Deliberately doesn't patch those files directly — users' Program.cses have auth, custom middleware, etc. we can't safely rewrite around.
• Prints a Spectre summary table + change list + next-steps footer.
• Interactive prompt for GitHub repo unless --yes is passed (which also silently accepts non-TTY stdin).

src/ShellDocs.CLI/Program.cs — swaps the placeholder init handler for InitCommand.Run(dir, yes, theme). Added a --dir option (defaults to cwd).

tests/ShellDocs.Tests/InitCommandTests.cs — 7 integration tests. Each spins up a temp dir with a minimal Blazor csproj, invokes InitCommand.Run via reflection, and asserts the outcome. Covers:

• Missing csproj returns error
• Non-Blazor csproj returns error
• Valid Blazor project scaffolds all expected files
• Package references get added to csproj
• Second run is a true no-op (byte-for-byte identical csproj + content)
• User modifications to scaffolded files are preserved on re-run
• Falls back to Pages/ when Components/Pages/ doesn't exist and Pages/ does

Test project now ProjectReferences ShellDocs.CLI for reflection access. Full suite: 78 passing (was 71, +7).

Smoke test (verified locally)

mkdir SmokeApp && cd SmokeApp
cat > SmokeApp.csproj <<'EOF'
<Project Sdk="Microsoft.NET.Sdk.Web">
  <PropertyGroup><TargetFramework>net10.0</TargetFramework></PropertyGroup>
  <ItemGroup><PackageReference Include="Microsoft.AspNetCore.Components.Web" Version="10.0.0" /></ItemGroup>
</Project>
EOF
shelldocs init --yes