refactor(worker): switch MCP config to env-var token expansion

BuildMcpConfigJson drops the token argument; the literal
\${CLAUDEDO_PLANNING_TOKEN} placeholder is written to mcp.json so
claude expands it from the spawned process environment at load time.
Also declares SettingsLocalJson constant for use in later tasks.

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

src/ClaudeDo.Worker/Planning/PlanningSessionManager.cs

@@ -86,7 +86,7 @@ public sealed class PlanningSessionManager
             Path.Combine(sessionDir, "system-prompt.md"),
             Path.Combine(sessionDir, "initial-prompt.txt"));
 
-        await File.WriteAllTextAsync(files.McpConfigPath, BuildMcpConfigJson(token), ct);
+        await File.WriteAllTextAsync(files.McpConfigPath, BuildMcpConfigJson(), ct);
         await File.WriteAllTextAsync(files.SystemPromptPath, BuildSystemPrompt(), ct);
         await File.WriteAllTextAsync(files.InitialPromptPath, BuildInitialPrompt(task), ct);
 
@@ -157,7 +157,7 @@ public sealed class PlanningSessionManager
             .TrimEnd('=');
     }
 
-    private static string BuildMcpConfigJson(string token)
+    private static string BuildMcpConfigJson()
     {
         var payload = new
         {
@@ -169,7 +169,7 @@ public sealed class PlanningSessionManager
                     url = McpServerUrl,
                     headers = new Dictionary<string, string>
                     {
-                        ["Authorization"] = $"Bearer {token}"
+                        ["Authorization"] = "Bearer ${CLAUDEDO_PLANNING_TOKEN}"
                     }
                 }
             }
@@ -177,6 +177,12 @@ public sealed class PlanningSessionManager
         return JsonSerializer.Serialize(payload, new JsonSerializerOptions { WriteIndented = true });
     }
 
+    private const string SettingsLocalJson = """
+        {
+          "enableAllProjectMcpServers": true
+        }
+        """;
+
     private static string BuildSystemPrompt() =>
         """
         You are a planning assistant for ClaudeDo.