feat(worker): add external MCP app-settings read tool

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/ClaudeDo.Worker/External/AppSettingsMcpTools.cs

@@ -0,0 +1,31 @@
+using System.ComponentModel;
+using ClaudeDo.Data;
+using ClaudeDo.Data.Repositories;
+using Microsoft.EntityFrameworkCore;
+using ModelContextProtocol.Server;
+
+namespace ClaudeDo.Worker.External;
+
+public sealed record AppSettingsReadDto(
+    string DefaultModel, int DefaultMaxTurns, string DefaultPermissionMode,
+    string WorktreeStrategy, string? CentralWorktreeRoot,
+    bool WorktreeAutoCleanupEnabled, int WorktreeAutoCleanupDays);
+
+[McpServerToolType]
+public sealed class AppSettingsMcpTools
+{
+    private readonly IDbContextFactory<ClaudeDoDbContext> _dbFactory;
+
+    public AppSettingsMcpTools(IDbContextFactory<ClaudeDoDbContext> dbFactory) => _dbFactory = dbFactory;
+
+    [McpServerTool, Description("Read the worker's app-level defaults (model, max turns, permission mode, worktree strategy). Read-only.")]
+    public async Task<AppSettingsReadDto> GetAppSettings(CancellationToken cancellationToken)
+    {
+        using var ctx = await _dbFactory.CreateDbContextAsync(cancellationToken);
+        var row = await new AppSettingsRepository(ctx).GetAsync(cancellationToken);
+        return new AppSettingsReadDto(
+            row.DefaultModel, row.DefaultMaxTurns, row.DefaultPermissionMode,
+            row.WorktreeStrategy, row.CentralWorktreeRoot,
+            row.WorktreeAutoCleanupEnabled, row.WorktreeAutoCleanupDays);
+    }
+}