test(worker): adapt planning tests to git-backed worktree flow

Update constructor calls (6-arg), seed AppSettings with sibling strategy,
git-init working dirs via GitRepoFixture.InitRepoWithInitialCommit, and
replace McpConfigPath assertions with worktree-path / .mcp.json checks.
Also fixes PlanningHubTests which had the same 3-arg constructor.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/ClaudeDo.Worker.Tests/Infrastructure/GitRepoFixture.cs

@@ -78,6 +78,21 @@ public sealed class GitRepoFixture : IDisposable
         return stdout;
     }
 
+    /// <summary>
+    /// Creates a new git repo at <paramref name="dir"/> with a seed commit.
+    /// Used by planning tests that need a real git repo as list working directory.
+    /// </summary>
+    public static void InitRepoWithInitialCommit(string dir)
+    {
+        Directory.CreateDirectory(dir);
+        RunGit(dir, "init", "-b", "main");
+        RunGit(dir, "config", "user.email", "test@claudedo.local");
+        RunGit(dir, "config", "user.name", "test");
+        File.WriteAllText(Path.Combine(dir, "README.md"), "seed\n");
+        RunGit(dir, "add", "-A");
+        RunGit(dir, "commit", "-m", "chore: seed");
+    }
+
     private static void ForceDeleteDirectory(string path)
     {
         if (!Directory.Exists(path)) return;