M2: the four V1 atoms + Git sync (Gitea / filesystem)

- Author the four V1 skill atoms in skills/ (Git is the source of truth): spec-writing &
  story-breakdown (product-owner), test-plan-generation & diff-review (qa) — each with
  risk-tagged actions, golden tests, and a body.
- SharedKernel: IGitProvider seam (read-only, provider-agnostic) + GitFile.
- Integrations module (its first real code): FileSystemGitProvider (dogfood/local) and a
  GiteaGitProvider (Gitea REST: recursive tree → SKILL.md blobs → base64 contents); the
  provider is chosen by GitSource:Provider config.
- Skills: SkillSyncService consumes IGitProvider (never Integrations) and indexes each file;
  POST /api/skills/sync and a POST /api/skills/webhook/gitea (re-sync on push; signature
  verification + changed-file-only + queue offload come later).

Verified: build green; ArchitectureTests 8/8 (Skills & Integrations reference only
SharedKernel; the Git seam lives in SharedKernel); IntegrationTests 22/22 incl. a sync that
indexes the four real atoms from skills/, published and queryable by role.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/Modules/TeamUp.Modules.Integrations/IntegrationsModule.cs

@@ -3,20 +3,33 @@ using Microsoft.AspNetCore.Http;
 using Microsoft.AspNetCore.Routing;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using TeamUp.Modules.Integrations.Git;
+using TeamUp.SharedKernel.Git;
 using TeamUp.SharedKernel.Modularity;
 
 namespace TeamUp.Modules.Integrations;
 
-/// <summary>BYOK API configs, the Git connection, the encrypted-credential store (M3).</summary>
+/// <summary>
+/// BYOK API configs, the Git connection, the encrypted-credential store. In M2 it provides the
+/// <see cref="IGitProvider"/> (filesystem for dogfood, Gitea over REST). BYOK lands in M3.
+/// </summary>
 public sealed class IntegrationsModule : IModule
 {
     public string Name => "integrations";
 
     public void Register(IServiceCollection services, IConfiguration configuration)
     {
-        // Skeleton: no services yet. M3 introduces this module's (internal) DbContext, the
-        // encrypted ApiConfig store, and the provider-agnostic model-client seam interface.
-        // The concrete model client (Microsoft.Extensions.AI) is deferred to M3-M4.
+        services.Configure<GitSourceOptions>(configuration.GetSection(GitSourceOptions.SectionName));
+        var options = configuration.GetSection(GitSourceOptions.SectionName).Get<GitSourceOptions>() ?? new GitSourceOptions();
+
+        if (string.Equals(options.Provider, "gitea", StringComparison.OrdinalIgnoreCase))
+        {
+            services.AddHttpClient<IGitProvider, GiteaGitProvider>();
+        }
+        else
+        {
+            services.AddSingleton<IGitProvider, FileSystemGitProvider>();
+        }
     }
 
     public void MapEndpoints(IEndpointRouteBuilder endpoints)